Tuesday, April 17, 2018

The GCE filters from DGM Optics

Possibly the best kept secret in nebula filters, the GCE filters from DGM Optics

I live in a heavily light-polluted area, right in one of the five boroughs of New York City. It's unfortunate; But, like other (dedicated) urban observers, I don't let it stop me from enjoying visual astronomy. For me, it's DSO's; In fact, it's almost always been DSO's for me. Except of course, for that first year... With the first small refractor kit - Back when I was 14 years old: During my first year of observing, I went for planets and the moon. Well, I'm 48 now - And I'm a confirmed chaser of faint fuzzies. It also seems that I appreciate and enjoy binocular astronomy more and more each year. I'm always on the lookout for that next instrument (usually Binos these days), or an accessory to help me fight light pollution. Generally, anything that will give me a bit of an advantage help me to locate and view fainter and fainter DSO's.

For a few brief years (while in my late 20's) I was fortunate enough to own and use some fine optical instruments: A TeleVue Pronto (70mm refractor), along with Televue and Takahashi EP's; Fujinon 7x50's & 16x70's - Both with proprietary screw-on Fujinon nebula filters, as well as an 8" Dobsonian with lots of nebula filters... I took a short "hiatus" from astronomy for a while (while pursuing other hobbies), and ended up selling all of my high-quality equipment.

Today, my equipment consists of the following: Bushnell 8x30's, Barska 15x70's, Garrett Signature Series 10x50's, Celestron 80mm Spotting scope (20-60x), Bushnell 5" Truss Tube Dob, Apertura AD8 8" Tweaker's Dream Dob, Standard Bushnell & Apertura EP's, Tripods, and lots of Nebula filters...
My latest accessory purchase, was a pair of unique "nebula" filters from a company called DGM Optics. Not only are these filters priced lower than many other companies' offerings - But, according to an excellent review I read, they perform better than filters from the other well-known companies!
I ordered a pair of their GCE filters for use on a couple of pairs of binoculars, etc., to help me in spotting DSO's.

GCE stands for Galaxy Contrast Enhancement! Neat, huh? Of course, I was initially very intrigued by them.
Well, it's true - I've seen it for myself now; using a pair of them on my Garrett Signature Series 10x50 binoculars (and also on EP's, with my 8" Dobsonian).
I have no affiliation with DGM Optics, by the way (aside from being a satisfied customer).
Here are the filters screwed onto the threaded eyepiece barrels of my 10x50's - This is basically their permanent location now.

As far as I know - These are the only filters currently in production, that are actually indicated for the image enhancement of galaxies! I think this is great! And although (as one would expect) the difference isn't jaw-dropping - So far, I have seen a noticeable improvement when viewing several of the brighter galaxies: M31, M51, M101. And I'm really looking forward to using them on many more (smaller & fainter) galaxies!
These filters are great for use on small aperture instruments - especially Binoculars. One of the reasons for this, is that they allow a generous amount of light through (while blocking light pollution, of course).

At a quick glance, they could be considered close to a 'Broadband' type of light pollution filter - As opposed to say, a UHC-type for example. I suppose the only popular filters that they could be compared to, would be the 'Deep Sky' types. However the GCE's actually do improve the view on galaxies in my heavily light polluted backyard.
I've never taken the time to accurately determine what the NELM is at my observing site. But, I would say it's about magnitude 4.5 (maybe 5.0, on a really good night!). Using the GCE filters on my Garrett 10x50's, mounted on a good Manfrotto tripod set, I've been able to see (and confirm) the following objects: The Rosette nebula, The Christmas Tree Cluster, The Eskimo Nebula (NGC 2392), IC 405 & 410, and Pk219+31.1. There are a few more faint nebula that I thought I may have seen, using averted vision - But, cannot confirm 100%, so I haven't listed them.
This was just during the first few weeks since their arrival.

The GCE's give all objects under observation an interesting hue of magenta. Sort of a pinkish/purple, that I happen to find pleasing. It doesn't seem to be as restrictive, or distracting as other nebula filters that I've used. Anyone who has an assortment of nebula filters in their collection knows what I'm referring to.

In addition to my 10x50's, they perform very well when carefully taped to the eyepieces of my cheap Barska 15x70's. I also use one with my 8" Dobsonian when scanning/searching for DSO's, using wide-field (30 & 25mm) 1.25" eyepieces. They work very well on my higher-power EP's also (10 & 9mm).

I was going over my Astronomy notes recently...And realized, that there are some interesting technical details about these nebula filters that I can share. This is info copied directly from DGM Optics, hence the quotations: My comments are italicized.

"The Galaxy Contrast Enhancement™ filter aids in the visual observation of galaxies and milky way dust clouds and dark lanes. The GCE filter takes a different approach to enhancing galaxy observation by allowing high transmission through nearly the entire visible spectrum while rejecting only the harmful light pollution wavelengths. Because of those attributes it also is a very good general purpose LPR filter, unlike traditional wideband filters, which exclude most of the red portion of the visible spectrum. - I like this very much, because until now, it seemed that you couldn't "have your cake & eat it too" - If you used a broadband filter, from other manufacturers, some of the desired wavelengths were getting blocked as well (especially the desired red).

"Specifications
The GCE filter design stresses maximum optical throughput utilizing state-of-the-art optical thin-film designs and materials. This filter is a “first surface” hard oxide thin-film and is much more durable and long lived than laminated “soft film” designs used by several famous makers." - I'm also very happy about this, no one wants a light pollution filter with a surface that will deteriorate over time.

"They are also much less prone to the internal reflectance problems that plague laminated filters. Laminated filters can produce a very undesirable “doubling” of stellar images often with one of the doubles being red. Contrary to popular belief, this image doubling is not due to the red sideband component that many nebula filter designs produce, but in many cases is due to laminated glass not being exactly parallel to the protective cover plate after lamination. Many laminated filters display this annoying characteristic." - After learning about this, why would anyone want to buy an inferior nebula filter again? I won't be!

"This filter averages around 1% Transmission (optical density of 2) through the rejection region from 540 to 590nm, and average transmission greater than 90% Transmission in the passbands, and greater than 75% at the 656.3nm H-Alpha line. The design yields a filter with a very symmetrical shape and high optical throughput, for maximum enhancement of nebula with a minimum of loss of stars in the field of view.
The substrate is quartz and has measured total wavefront values of .25 waves. - I find this fact awesome. These filters don't use plain glass as their substrate; it's Quartz!
The combination of first surface optical thin-film technology and a polished, flat substrate enables this filter to be used with high magnification, a real plus for small planetary nebula." - And, finally, this last part - about being "a real plus for small planetary nebula" It just so happens, that I have become very interested in hunting planetary nebula recently So, I was also happy to read this.
If there is any area that has room for improvement, it would be with the (1.25") metal filter housing. The small notches on the outer diameter of the filter housing: These serve to provide a better grip, or traction for a user's fingertips (while screwing the filters on or off of EP's). It would be nice, if they could be made to be less likely to slip between fingertips. My other nebula filters seem to be easier to hold on to, by allowing fingertips to gain a firmer grip. The actual filter cells on these GCE's could be considered "low-profile" when compared to the Zhumell brand filters, for instance.


As for me: One of the joys of using this GCE filter - Is that I simply leave a pair of them screwed into the threaded EP barrels of my Garrett signature series 10x50's - And, I just leave them attached all the time. I don't find my views of Asterisms, or Open Clusters darkened very much at all. Yet, they improve the views of all DSO's at same time. They constantly help me to detect nebulas (of all kinds), which I simply could not/would not see without the filters in place. I've actually tested this quite a few times.

It would be great, if someone who has other name-brand "Broadband" LPR filters (or DeepSky/SkyGlow types) could also do some tests verses the GCE filter...
The smallest (good-quality) binoculars I currently have, are my Garrett 10x50's. But, I believe these filters would also perform well on smaller Binos (if one were willing to experiment) - Which would be great when scanning for/observing even larger, diffuse DSO's. In fact, I believe I just gave myself an idea for a future project...
In conclusion, I just wanted to share my experiences. I happen to be a huge fan of binocular Astronomy (and nebula filters!). And, hope that fellow Astronomers, who have similar interests, will find these GCE's to be a useful addition to their equipment.

Clear skies!
-Al

Sunday, April 15, 2018

Electronically Assisted Astronomy...

I just stumbled upon this gentleman's site.
And absolutely love his work; especially his writing.

He very eloquently (and amusingly) describes the typical plight of urban amateur astronomers. I've recently become very interested in EAA, and just learned of the existence of this software.

He is the creator of AstroToaster - An extraordinary camera controlling application, that anyone interested in EAA will eventually discover. As for me, I'm very excited about it, and will be going back to that Site right now; to absorb everything I can about this (relatively) new method!

Much more to follow (when I'm on an actual keyboard).

Clear skies!


Friday, March 30, 2018

Inspiration For Urban Astronomers - Especially Astrophotographers!

My Brothers, Louis & John, sparked my interest in binoculars & telescopes at a young age. 
Later, my Brother John bought me my first telescope, I believe it was for my 14th birthday. It was a small refractor, and I've been lovin' Astronomy ever since. I'm 48 now.

I've never let the fact that I now live in an urban area stop me from enjoying Astronomy. Why should I?
I'll admit, I've become pretty frustrated in the past. Even took a hiatus from the hobby, several times. 
But the important thing is to keep coming back...

I just stumbled across this gentleman's YouTube channel, and I love this 1st video. It exemplifies what real urban amateur Astronomers go through: Garnett Leary

More to follow...

Clear skies!

Friday, November 6, 2015

A Document On Nebula Filters, And A Book On Astro Sketching

I've always been a huge Fan of the light pollution filters made by Omega Optical (I usually order them from DGM Optics). If interested, check-out This great PDF document (found via the "Mega-Nebula Filter Site" linked to above).

----- I'd like to take this opportunity, to just briefly mention a new must-have book!
I'll write a full Review of it here, for the blog, in the near future. -----
So, just the bare minimum for now:

I'm very happy to report, that Rony De Laet, an amatuer Astronomer who's work I've greatly admired for many years - Has written a book! 'The Casual Sky Observer's Guide'
I bought (the electronic version of) it immediately! And, I simply love it!
I highly recommend it! (Hopefully, Santa Claus will bring me a paper version of the book for Christmas?)

I have been following his impressive, and very inspiring Website for many years...
Besides the fact, that the Author is obviously a binocular fanatic (like me!) -- He also produces amazing and inspiring pencil sketches! Using Binocs, of course!

In a nutshell: What impresses me most, is his minimalist approach in regards to equipment.
He has been able to do all of this, mainly with just two pairs of binoculars. Two pairs, of what many amateur Astronomers might consider modest binocular models. In other words, not "Alpha" model or super-expensive units.
A pair of 8x56's and a pair of 15x70's (along with a SkyWindow mirror mount).
Very inspiring.

It is basically something that I would love to be able to do: Choose just two pairs of binoculars, to be used for any and all observing (and sketching).
In fact, I'm working on doing just that...
I've always seemed to be spending too much time comparing the performance of various binoculars -- Instead of simply investing in two good pairs, and using them (instead of always scrutinizing their optical abilities).

To be continued...

Incidentally, I've noticed that The SkyWindow looks like it's available for order
once again - The Website was undergoing renovations for a while there... 

Clear skies!

Friday, October 30, 2015

VHT Nebula Filters From DGM Optics

The VHT Nebula Filters from DGM Optics - First impressions

Just a short Post, for now.

You can see the full line of (1.25") nebula filters available, from DGM Optics Here Of course, they are also available for 2" eyepieces.

As I mentioned in my previous Post: The pair of Garrett Optical 100mm binoculars were in need of some nebula filters...More specifically, the pair of (stock) 1.25" eyepieces needed filters. And, I wasn't 100% sure which types I would go with, this time around. These binoculars are much larger than any pair I've used before.

I was originally thinking: A pair of (1.25") GCE's (again)... Unless, (I thought to myself) after consulting Dan: He might suggest something different this time? Perhaps NPB's? I was anxious to find out.
Well, I did ask Dan (of DGM Optics [via e-mail]) and he recommended The VHT's. And it made a lot of sense to me. Here's a Link to the Info page, for the various filters.

Here is the transmission curve, from Omega Optical, the manufacturer: 



Also, from Omega Optical's Site regarding The VHT's:

"An excellent Nebula filter for smaller scopes (4-6 inches aperture) where light gathering and throughput are at a premium. It is also quite effective with larger scopes."

I have been very intrigued, with the measured spectral information shown here on DGM's page. The white graph on the lower right is of GCE Filter.
I also can't help wondering exactly what the measured spectral results would be, for my actual filters. That would be neat.

I haven't had many nights of good seeing, in which to thoroughly test them - But so far, the VHT's have been able to boost the contrast, on the few nebulae that I've tried them on.

And, finally, for astrophotographers - Here are some examples of how these filters help when imaging.
You'll see links to some Reviews of DGM nebula filters Here.

I plan to post a short Review of these filters here, in the near future.

Clear skies!

Tuesday, September 22, 2015

The Bortle Scale - Route 6 In Cortlandt NY -

The Bortle Scale - Bright suburban skies, and Route 6 In Cortlandt NY -

   Image credit: created with the free software Stellarium, retrieved from Sky & Telescope.

I'm happy to report a short, but successful "mini-field-trip" to Cortlandt New York, courtesy of my BIL, Nelson. It was the first outing for my recently acquired Binocs:

The Garrett Optical 100mm binocular telescope
-and-
The New 12x60 handhelds, from Oberwerk.

Nelson enjoyed, and remarked about the abundant FOV in the 12x60's (compared to the narrow FOV of the big Garrett's). 

Among the objects observed, were: 
M31 - The Andromeda Galaxy
M33 - The Pinwheel Galaxy
The Double Cluster in Perseus -
(NGC 869 [h Persei] and NGC 884 [Chi Persei])

And, The Milky Way looked great!

I went ahead, and set-up Google Earth, as was described on the very interesting (if somewhat eclectic Page) Here

According to this neat new map - My local skies, here at home, are:

Bortle 6   Bright suburban sky 5.1-5.5
  • the zodiacal light is invisible
  • light pollution makes the sky within 35° of the horizon glows grayish white
  • clouds anywhere in the sky appear fairly bright
  • surroundings are easily visible
  • the Milky Way is only visible near the zenith
  • M33 is not visible, M31 is modestly apparent
  • limiting magnitude with 12.5" reflector is 14.5

If this overlay technique is accurate, then my local light pollution is just about as "good" (maybe even half a magnitude better) than I had originally guesstimated. And I'm really happy about that...

If this is in fact, the case - Then I'll take it! I can work with 'Bright suburban sky'
*Correction* - I am, in fact, in a White Zone... *sigh*
What was I thinking?

Light pollution link.

What this all actually translates into now, for me...Is that I will (eventually) have to confirm this map's accuracy. By "manually" checking the naked-eye visibility of several different constellations / stars, etc.

According to this map, the skies (which I thought were awesome) during a recent Astro-outing, in Cortlandt New York, are:


Bortle 5   Suburban sky 5.6–6.0
  • only hints of zodiacal light are seen on the best nights in autumn and spring
  • light pollution is visible in most, if not all, directions
  • clouds are noticeably brighter than the sky
  • the Milky Way is very weak or invisible near the horizon, and looks washed out overhead
  • limiting magnitude with 12.5" reflector is 15
 Clear skies!

Saturday, September 19, 2015

Finally: A Binocular Telescope!

I'm very happy to have "picked up" visual Astronomy observing again.

F/5.3 100mm Garrett Optical

I finally managed to get a nice pair of (early model) Garrett 100mm Binocs. And, I'm going to need a new pair of nebula filters for them.
I was shopping around, just looking, etc. 
But, it didn't take long for me to realize, that I'd be best off with a pair from DGM Optics! Duh!

So, my next Post, will be about the selection and use of nebula filters for this instrument...
Along with a short review.

Clear skies!

Sunday, September 13, 2015

Visual Observing Has Commenced Once Again!

I'm very happy to be posting on this blog once again...

Thanks to the generosity (and Herculean effort) of two very dear Friends - I'm now the proud owner, of my very own 8" Cat (SCT Telescope).
A rare, Bausch & Lomb 8001 Schmidt-Cassegrain, with (sidereal) motor drive.

The complete restoration, and collimation of the optics, is still a work in progress...
The first few phases have been completed -

Below is a quick Pic of the telescope.


In the meantime, I've started observing/sketching again (using my Barska 15x70's); and having a lot of fun!
 
 Clear Skies!

Saturday, December 15, 2012

Star Atlases: The Good, The Bad, And The Not-So-Good...

Just a quick heads-up: I recently purchased some "printed Astronomy materials" - A few books and...Star Atlases, etc. Including the 'Bright Star Atlas' 2000.0 by Wil Tirion: I bought it, because I read a recommendation for it, on some binocular Astronomy site (I believe).
From what I read, it was supposed to be great...Well, the fact is, I don't happen to like it very much... It seems as though there are many Deep Sky Objects missing/not shown.

I'm not sure "what happened" when this atlas/book was produced; because other publications that Wil Tirion has worked on are excellent! So, I don't get it..

Luckily, it was only ~ $14 (shipped) from Amazon. So, first & foremost, I just wanted to start with this one: It's on my "Not-So-Good List" 


On the other hand, 'The Pocket Sky Atlas', from Sky&Telescope - Is awesome! Excellent images, useful Legends and measuring scales. One of them, represents a Telrad sight. The atlas is spiral-bound, and conveniently sized. I use it all the time, as my main sky chart. Nice, accurate, and detailed:

...Beautiful cover too! :)

And, another really good publication -
Binocular Highlights: 99 Celestial Sights for Binocular Users (Sky & Telescope Stargazing) [Spiral-bound]

Being a die-hard binocular Astronomer, I really love this book! Highly recommended...I can't say enough good things about it. It is a delight. For example: I really love how Gary Seronik simply comes right out and states, that 10x50 binoculars are, in fact the best size to get (and why). Outstanding!

I recently noticed, that another favorite Author of mine (Stephen Tonkin) also recommends 10x50's as the best size overall... And, one of his most awesome books, is now in it's Second Edition - It is simply a must-have!

 

Clear skies!

Sunday, November 25, 2012

The Best Kept Secret In Nebula Filters! DGM Optics!

Just a quick post, to let you know, that I've ordered a pair of innovative new "nebula" filters from a company called DGM Optics. http://www.dgmoptics.com/ Not only are these filters priced lower than many other companies' offerings - But, according to the excellent reviews (on Astronomy forums, etc.) they perform better than filters from the other well-known companies! (It's true - I've seen it myself now, using my 8" Dob). You can check out this Link , to order filters. OIII filters are currently on sale!
I have ordered a pair of their GCE filters for use on a couple of pairs of binoculars, for spotting DSO's.
CGE stands for Galaxy Contrast Enhancement! Neat, huh? These are the only filters currently in existence, that are actually indicated for the image improvement of Galaxies! I think this is great, and I'm really looking forward to receiving them! A full review will be posted up in the near future!

Check out the transmission plot:

...Very interesting...
Here is their e-bay Link where you can read more about these, and other filters. Their NPB - Narrow PassBand nebula filters have been tested & compared by several experienced amateurs - And the general consensus is, that they are the best contrast-enhancing nebula filters currently available!

And, here is a Link to a full review/comparison done with the GCE filter by an expert, on the CloudyNights Web site. Since originally starting this post, The filters have actually arrived, and I even got a chance to test them; a little bit...The filters were shipped out to me on Monday; and arrived on Wednesday. Since we've got a full moon, I wasn't able to really check out their performance. But, I screwed both filters onto the threaded EP barrels of my brand-new 10x50 Garrett Signature Series binocs. And, they seem to: Darken the background sky, Allow a nice amount of light through (compared to OIII's for example), And I like the way they render most stars a hot purple-ish hue (it's a nice change from the usual green of other filters).
These GCE filters are perfect for binocular use! 


Dan, of DGM Optics is dedicated to his customer's happiness. It's not only obvious, but very nice of him to be very accommodating. . And, I appreciate it a great deal.
So, I can report that ordering/dealing with Dan at DGM Optics, has been a pleasure. Keep an eye on their Website, their VHT Nebula filters should be going on sale soon! 

Clear skies!