Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

light pollution or UHC filter for 80mm aperture

  • Please log in to reply
15 replies to this topic

#1 pygmycory

pygmycory

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 16 May 2018
  • Loc: Victoria BC Canada

Posted 17 June 2018 - 10:14 PM

I live in a highly light polluted (bortle 8) area, and have an 80mm F5 achromatic refractor. I am considering getting either an UHC, or a broadband/light pollution filter in hopes of being able to see deep sky objects better, especially nebulae. I am wondering if a filter of this type is useful on a telescope this small, or if it would cut out too much light. I am mainly looking at these three possibles:

http://quarkyscience...on-filter-1-25/

http://quarkyscience...hc-filter-1-25/

http://quarkyscience...ow-filter-1-25/

 

I'm not expecting miracles, just improvement, especially given that the streetlights round here are LED, and I have a budget of CAN$75.

 



#2 Augustus

Augustus

    Fly Me to the Moon

  • *****
  • Posts: 6742
  • Joined: 26 Dec 2015
  • Loc: Connecticut

Posted 17 June 2018 - 10:21 PM

I would just save your money for a bigger scope. 


  • nicoledoula likes this

#3 pygmycory

pygmycory

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 16 May 2018
  • Loc: Victoria BC Canada

Posted 17 June 2018 - 10:21 PM

I should mention that this is for visual viewing.



#4 Procyon

Procyon

    Fly Me to the Moon

  • *****
  • Posts: 5481
  • Joined: 23 Feb 2009
  • Loc: Eastern Canada

Posted 17 June 2018 - 10:28 PM

I'd skip 1 and 3 and get a nice UHC filter such as this one https://www.eyepiece...ctCode=14501010 which is actually one of the best if not best one, and very well priced on top of it. The newly released Lumicon UHC is supposed to be great also!

Afterwards, once it arrives, if you really want to see Nebulae much better with the UHC filter, drive to any gas station, add some gasoline, and drive off to a dark site of your choice. Use Google and search for a light pollution map or join a local astronomy club to also get access to their dark sites.

smile.gif


Edited by Procyon, 18 June 2018 - 10:11 AM.

  • MortonH and Ernest_SPB like this

#5 havasman

havasman

    Cosmos

  • ****-
  • Posts: 8249
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 17 June 2018 - 11:05 PM

Modern light pollution has a wider bandwidth than the old days when those LP filters were developed and they are now largely obsolete.

A good UHC filter will be much more effective. But nothing will help more than observing from a darker site.


  • Jon Isaacs, MortonH, Ernest_SPB and 2 others like this

#6 macdonjh

macdonjh

    Gemini

  • *****
  • Posts: 3275
  • Joined: 06 Mar 2006

Posted 18 June 2018 - 09:33 AM

+1 for a dark site with an 80mm scope.

 

A UHC filter rejects a lot of light.  I've never tried on in an 80mm scope, but my guess is your view will be very dim.  I got tired of being disappointed by the view of deep sky objects when viewing from my driveway, so when I'm home I only observe the moon, planets and double stars.  I save the other deep sky objects for trips to my club's dark sky site.


  • Augustus and nicoledoula like this

#7 faackanders2

faackanders2

    Fly Me to the Moon

  • *****
  • Posts: 5524
  • Joined: 28 Mar 2011

Posted 18 June 2018 - 12:31 PM

I live in a highly light polluted (bortle 8) area, and have an 80mm F5 achromatic refractor. I am considering getting either an UHC, or a broadband/light pollution filter in hopes of being able to see deep sky objects better, especially nebulae. I am wondering if a filter of this type is useful on a telescope this small, or if it would cut out too much light. I am mainly looking at these three possibles:
http://quarkyscience...on-filter-1-25/
http://quarkyscience...hc-filter-1-25/
http://quarkyscience...ow-filter-1-25/
 
I'm not expecting miracles, just improvement, especially given that the streetlights round here are LED, and I have a budget of CAN$75.

Always go with UHC (Ultrablock) for planetaries and emmission nebulae. OIII cuts out many stars and skyglow does not blacken background enough.
Orion always has filter sales after XMAS.

#8 Adun

Adun

    Vanguard

  • *****
  • Posts: 2339
  • Joined: 02 Dec 2016

Posted 18 June 2018 - 01:41 PM

I live in a highly light polluted (bortle 8) area, and have an 80mm F5 achromatic refractor. I am considering getting either an UHC, or a broadband/light pollution filter in hopes of being able to see deep sky objects better, especially nebulae.

 

I am wondering if a filter of this type is useful on a telescope this small, or if it would cut out too much light.

 

Both:

 

Useful: From bortle 8 skies (like mine), the UHC filter makes the difference between seeing and not seeing some less bright (but still bright) emission nebula (like M27). Still, you won't see as much detail in nebula as you would with the same scope under Bortle 2 skies.

 

Cuts out too much light: At this aperture, the loss of light is noticeable. Under your bortle 8 skies, with the filter many stars will become very very faint and star hopping will be unpleasant. The same filter, under the same bortle 8 skies works much better on my 10" dob.

 

 

From my own experience, my 80mm F4.4 achromat (an Orion GoScope) benefits a lot more from traveling to a dark site than from a filter. It gave me unbelievably good views of M42, Andromeda and Carina Nebula when I took it to a Bortle 2~3 remote beach, those amazing views still haunt me.

 

So, an UHC filter will help for the brighter emission nebula but barely. Given the strength of an 80mm ~F5 achromat is it's ability to travel, take it somewhere dark. It'll show you so much more from nebula and galaxies if you take it to a truly dark site.


Edited by Adun, 18 June 2018 - 01:47 PM.


#9 pygmycory

pygmycory

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 16 May 2018
  • Loc: Victoria BC Canada

Posted 18 June 2018 - 02:07 PM

I will be doing some dark site observing in August or September, when I visit family, and likely more locally. That is one reason I went for such a small scope in the first place. Right now, the short nights, no car, and fact I'm female make me unwilling to go running around on the bus when I wouldn't get home till well after midnight. I've been doing most of my observing when I wake up at 2 or 3am, as I do many nights. I have been able to see more than I feared from my backyard, and love my telescope.

 

I can make out the lagoon nebula, and am looking for something that will allow me to see it and similar items better. I would also take the UHC filter with me if/when I go to a darker site, and concentrate on hunting down things like nebulae and galaxies that are difficult or impossible at home - as well as showing off the planets to my parents, of course!

 

How much it would a UHC filter dim the image in a scope this size? I believe most UHC filters are designed with bigger telescopes in mind. It sounds like people are recommending the UHC over a light pollution filter, which is good to know.



#10 faackanders2

faackanders2

    Fly Me to the Moon

  • *****
  • Posts: 5524
  • Joined: 28 Mar 2011

Posted 18 June 2018 - 02:19 PM

I will be doing some dark site observing in August or September, when I visit family, and likely more locally. That is one reason I went for such a small scope in the first place. Right now, the short nights, no car, and fact I'm female make me unwilling to go running around on the bus when I wouldn't get home till well after midnight. I've been doing most of my observing when I wake up at 2 or 3am, as I do many nights. I have been able to see more than I feared from my backyard, and love my telescope.
 
I can make out the lagoon nebula, and am looking for something that will allow me to see it and similar items better. I would also take the UHC filter with me if/when I go to a darker site, and concentrate on hunting down things like nebulae and galaxies that are difficult or impossible at home - as well as showing off the planets to my parents, of course!
 
How much it would a UHC filter dim the image in a scope this size? I believe most UHC filters are designed with bigger telescopes in mind. It sounds like people are recommending the UHC over a light pollution filter, which is good to know.

Recommend you join an astronomy club which may have a semi-private site, to observe with others to feel safer at a dark sky site.

#11 Adun

Adun

    Vanguard

  • *****
  • Posts: 2339
  • Joined: 02 Dec 2016

Posted 18 June 2018 - 02:24 PM

I can make out the lagoon nebula, and am looking for something that will allow me to see it and similar items better. I would also take the UHC filter with me if/when I go to a darker site, and concentrate on hunting down things like nebulae and galaxies that are difficult or impossible at home - as well as showing off the planets to my parents, of course!

 

How much it would a UHC filter dim the image in a scope this size? I believe most UHC filters are designed with bigger telescopes in mind. It sounds like people are recommending the UHC over a light pollution filter, which is good to know.

 

On a UHC filter, light transmission is very high for the right frequencies. This means that for bright nebula such as M42, M8, and Carina, your view of the fuzzy parts will not feel feel dimmer at all.

 

But other parts of the sky that carry light in other frequencies (such as stars) will dim considerably. This would affect galaxies, and perhaps some reflection nebula (like the faint part of M20).

 

An UHC filter is still the best one to use from bortle 8 skies, even with an 80mm scope. But I took my UHC to the afforementioned beach, and believe me: it wasn't needed there



#12 pygmycory

pygmycory

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 16 May 2018
  • Loc: Victoria BC Canada

Posted 18 June 2018 - 02:45 PM

I have turned up at the local astronomy society meetings, but their dark sky site (with access to a serious observatory!) is not somewhere I can get to by bus. It is possible I could talk someone into give me a ride to and from at some point, but I haven't done this yet, and the meetings have stopped over the summer. I'd also need to formally join, which is $80/yr. I would need to get to know one or two of them better, then ask. Which won't happen before september, since meetings have stopped.

 

If I get a filter, which I probably will, I'll go with a UHC.


  • Adun likes this

#13 astroclint

astroclint

    Vostok 1

  • -----
  • Posts: 141
  • Joined: 14 Jun 2017
  • Loc: Parker Colorado

Posted 19 June 2018 - 10:03 PM

You could get a cosmetic second from dgm which is cheap.

https://www.amazon.c...osmetic seconds



#14 Javier1978

Javier1978

    Apollo

  • *****
  • Posts: 1172
  • Joined: 12 Feb 2009
  • Loc: Buenos Aires, Argentina.

Posted 20 June 2018 - 05:27 AM

I use an astronomik UHC with my 80mm ST with great results, both in dark and polluted skies. It works really well for large nebulas and even large planetaries like M27 or the Helix. It's not aperture but exit pupil and finding the right target what matters.

#15 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 72552
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 20 June 2018 - 05:51 AM

+1 for a dark site with an 80mm scope.

 

A UHC filter rejects a lot of light.  I've never tried on in an 80mm scope, but my guess is your view will be very dim.  I got tired of being disappointed by the view of deep sky objects when viewing from my driveway, so when I'm home I only observe the moon, planets and double stars.  I save the other deep sky objects for trips to my club's dark sky site.

 I use UHC, O-III and H-beta filters in 80mm scopes all the time.  I even use them in my 50mm finder.  

 

Filters do reject a lot of light, that is exactly why you use a filter, it rejects the light you do not want, it passes the light you do want.  The Lagoon nebula is very rich in O-III.  Using a filter rejects the vast majority of the sky glow, dramatically increasing the contrast on the nebula itself.  Stars will also be reduced in brightness, the purpose of a nebula filter is to improve the views of nebulae and for that they are very effective, even is small scopes if used properly.

 

If you figure that a good O-III filter has a band pass of about 14nm and the visual spectrum is about 200nm, the contrast of an object like the Veil or the Lagoon will be improved by as much as 3 magnitudes.   A good UHC filter could reduce the skyglow by about 2 magnitudes..  This translates into views that are similar to a dark site.  

 

My backyard in San Diego is red-zone, on a good night, it is about 18.6 mpsas directly overhead, that's translates to something like magnitude 4.5 NELM.  Three magnitudes reduces the sky glow to 21.6, two magnitudes, to about 20.6.  As one might expect, this means that nebulae are much more easily seen. 

 

I have seen both the Veil and the Helix nebulae from my backyard in an 80mm scope.  One of the keys is not using too much magnification.  The brightness of the sky glow and the nebula itself depends on the exit pupil one employs, at a 5 mm exit pupil in an 80mm (that would be 16x), the image of the nebula is just as bright as it would be in a 400mm telescope with that same 5mm exit pupil.. The difference is that in the 400mm scope, the object will be magnified 80 times rather than 16 times. 

 

Nebula filters do work from urban skies in 80mm telescopes.    

 

As far as observing deep sky objects from an urban sky.. I enjoy it.  It's not like observing them from dark skies, which I am fortunate to do a week to two weeks per month.  But I take what I can get, with a cup half full, there can be plenty to see and observing under light polluted skies is good practice.  

 

How much it would a UHC filter dim the image in a scope this size? I believe most UHC filters are designed with bigger telescopes in mind. It sounds like people are recommending the UHC over a light pollution filter, which is good to know

 

.As you can see, UHC filters, O-III filters, they are designed for scopes of all apertures.  They only work on certain specific objects but for those objects, they are spectacular.  

 

Don Pensack (Starman1) has a comprehensive Filters Buyers Guide at the top of this forum, it's a good read.  

 

https://www.cloudyni...r-buyers-guide/

 

Looking at the Olivion 1.25 inch UHC filter, it looks to be quite reasonable, especially considering the $53 price.  It has a bandwidth of 30nm, very similar to the Orion Ultrablock which has a 29nm bandwidth.

 

Jon


  • Javier1978, Procyon and pygmycory like this

#16 pygmycory

pygmycory

    Vostok 1

  • -----
  • topic starter
  • Posts: 135
  • Joined: 16 May 2018
  • Loc: Victoria BC Canada

Posted 20 June 2018 - 09:43 PM

Jon, thank you for the very detailed explanation of what you've experienced using filters on small scopes under urban skies. Very helpful.


  • Jon Isaacs likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics