5 replies to this topic

[Whiteduckwagglinginspace]

Dear members,

I'm a brand new member on this forum, posting here for the first time.
I'm a Dutch guy (when making language errors...that's why), 48 years young and living in Norway - in the middle of nature at bortle 3. Never saw the milky way so bright and clear, when living in Holland.

Not only new on this forum, but also new in the hobby: 2 weeks ago I bought a Celestron Starsense dobsonian 8 inch as an first telescope (not pleased with the starsense-app), together with Celestron X-cel LX eyepieces (25, 9, 7 mm), X-cel barlow (2x) and two filters: an UHC filter (Sky Watcher) and the Baader Neodymium Moon & Sky Glow filter. 

Yesterday, I had finally (autumn and rain...) clear sky and could use my telescope for the very first time. I saw the GRS for the first time in my life and the Orion Nebula was beautiful! But....when using the UHC filter on the 25 mm, I did not see more of the Nebula, but less. I know stars can get dimmer and everything went green, but I did not expect to see less(!) of the Nebula. The more, because Mr. Knisely made a filter list, mentioning that an UHC filter should be very effective on the Orion Nebula.

My question....is it me doing something wrong or is it the Sky Watcher UHC which is giving very poor images?
Anybody here with the same filter or experience with this filter? 
I couldn't found proper information from other users yet on the internet.

At first, I wanted to buy the Astronomik UHC filter, but at the closest seller I could find (Denmark), the filter was out of stock. Because I didn't want to wait a long time, I hoped the Sky Watcher would be good enough.





 

Edited by Whiteduckwagglinginspace, 02 November 2024 - 07:47 PM.

[havasman]

Your perceptions are excellent and your questions are relevant. M42 is a very high amplitude very broad spectrum emitter. Nebula filters work well by removing energy at selected frequencies. So with M42 sending so many frequencies, removing any will generally dim the object. Most experienced observers prefer observing it without filter. As you have correctly seen, the most information is received that way. Your filter is working or you would not have seen what you did. Many other emission nebula will be better resolved by the actions of good nebula filters as they emit in narrower spectra than M42.

 

An O-III or Hb nebula filter removes different energies from a view of M42, always dimmer. But it is very interesting to see the emphasis on different areas and structures in the grand object.

 

You have done well to access Mr. Knisely's work. It is the standard reference and highly recommended. But, as with many other choices in the hobby, experimentation and belief in what YOU SEE should be your standard reference final authority.

Edited by havasman, 02 November 2024 - 08:06 PM.

[NiteGuy]

In my experience with M42, nebular filters simply don't work very well on this spectacular object. They'll help with the fainter extremities but at the expense of degrading the rest of the nebula. In general, a UHC filter will give the most obvious improvement to objects when you're under a bright, light-polluted sky.

 

Try your UHC on the Flame Nebula (NGC2024). It's about 1/2-degree above and slightly left of the leftmost belt star in Orion. It's no M42 but it should show some nice detail in your 8-inch and the UHC should show an improvement vs. without it.

 

Also, try the UHC on the Veil Nebula in Cygnus. The Veil has several parts and is a great object. Bright sky, dark sky, it doesn't matter, O-III filters really make this object come alive...from almost invisible, it's like someone flipped on a light switch...wow!.

 

IT'S IMPORTANT to know that ALL nebular filters require an extra bit of dark adaptation. Not so much with the UHC (about 1-minute) but a lot with an O-III (up to 3 minutes before you can see EVERYTHING). An Ha filter (mostly for the Horsehead Nebula) is insane...first look all you see is black...keep looking...3, 4, 5 minutes and then you might be able to see the indentation in the bridge of the nose on the horse's head!)

 

Just keep your eye at the eyepiece, be very patient, and your filter will reward you.

[Whiteduckwagglinginspace]

Havasman:

So, the Orion Nebula is a broad spectrum emitter.
A surprising anwer, I would never guess beforehand.
So, these are the kind of things a newbe doesn't know...  

Your explanation is very clear and it completely explains my experience with the UHC filter.
Thank You very much! I will never use a filter on the Orion Nebula again. Actually, there is no need for one, because it allready did a very(!) good, sharp en beautiful job in my eyepiece.

While apparently doing his (Sky Watcher UHC) job just fine, I'm still curious if the Astronomik filter is a much(?) better UHC filter though. Hopefully someone here had the opportunity to compare these two filters, because there seems to be very few information to find about how good this Sky Watcher filter really is.  

EDIT:

NiteGuy: thank You for Your advice about where and how to look. Really appreciated!
 

Edited by Whiteduckwagglinginspace, 02 November 2024 - 09:18 PM.

[havasman]

While apparently doing his (Sky Watcher UHC) job just fine, I'm still curious if the Astronimik filter is a much(?) better UHC filter though. Hopefully someone here had the opportunity to compare these two filters, because there seems to be very few information to find about how good this Sky Watcher filter really is.  

Importantly, a high amplitude emitter too.

 

I am not familiar with the Sky Watcher UHC but Don Pensack's 2024 nebular filters guide lists it with 28nm bandwidth versus the Astronomic UHC's 24nm. That is a relatively small difference and the performance you saw supports the SW's relative capability. My Lumicon's bandwidth per that resource is 26nm and it has been a standard for a long time. The fine Televue Nebustar UHC II (supplied to them by Astronomik) filter is listed as having a 27nm bandwidth. I'd say you're good. Perhaps you might look at an O-III filter next. That filter selects different bandwidths to block and is effective on a different group of emission nebulae, primarily planetary nebulae. An O-III is probably the best complement to a UHC filter. Between the two most emission nebulae are effectively rendered with higher apparent contrast as you have likely seen in the Prairie Astro articles Mr. Knisely wrote.

 

By all means you should use all your filters to observe M42. Just because it's an interesting exercise that well illustrates the functions of nebula filters. And because it's fun.

 

Here's Pensack's nebula filters guide -  https://www.cloudyni...s-buyers-guide/

 

Generally Astronomik, Lumicon and Televue are preferred nebula filter suppliers with all three equally effective in most situations and mostly without peers. Your SW is apparently an exception to the w/o peer part.

Edited by havasman, 02 November 2024 - 09:40 PM.

[Whiteduckwagglinginspace]

Importantly, a high amplitude emitter too.

 

I am not familiar with the Sky Watcher UHC but Don Pensack's 2024 nebular filters guide lists it with 28nm bandwidth versus the Astronomic UHC's 24nm. That is a relatively small difference and the performance you saw supports the SW's relative capability. My Lumicon's bandwidth per that resource is 26nm and it has been a standard for a long time. The fine Televue Nebustar UHC II (supplied to them by Astronomik) filter is listed as having a 27nm bandwidth. I'd say you're good. Perhaps you might look at an O-III filter next. That filter selects different bandwidths to block and is effective on a different group of emission nebulae, primarily planetary nebulae. An O-III is probably the best complement to a UHC filter. Between the two most emission nebulae are effectively rendered with higher apparent contrast as you have likely seen in the Prairie Astro articles Mr. Knisely wrote.

 

By all means you should use all your filters to observe M42. Just because it's an interesting exercise that well illustrates the functions of nebula filters. And because it's fun.

 

Here's Pensack's nebula filters guide -  https://www.cloudyni...s-buyers-guide/

 

Generally Astronomik, Lumicon and Televue are preferred nebula filter suppliers with all three equally effective in most situations and mostly without peers. Your SW is apparently an exception to the w/o peer part.

Thank You very much for your detailed explanation! What a helpfull forum with a lot of knowledge this is. Actually, I wanted to purchase the OIII filter first, but then i heard that an UHC filter should be Your first choice. Of course, I can buy all the filters (and other things) at once, but try to tell this to my wife...

So I guess my Sky Watcher UHC filter is (despite the fact that it was not expensive) a good filter and no need to change it for an Astronomik UHC filter. (My wife will be even happier then me.) 

Edited by Whiteduckwagglinginspace, 02 November 2024 - 10:12 PM.