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Old 23-10-2012, 06:05 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Time for some filters, any suggestions?

Hi,

I'm imaging with an unmodded canon 1100D, and it's time to consider some filters.

I see the astronomik clip filters for canons, and realise I need to go for longer exposures to compensate for an unmodded camera.
That does'nt worry me!
So what would be a good starting set?
Particularly interested to hear from others that are running unmodded camera's with filters.

Any feed back will be appreciated.

Cheers,

Justin.
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  #2  
Old 23-10-2012, 06:54 PM
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cometcatcher (Kevin)
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Hi Justin, I run an unmodified Pentax K-x. The lack of Ha response can be partially made up for by using a good nebula filter like the Astronomik CLS, Baader UHC-s or Lumicon Deep Sky. The Deep Sky and CLS allow about 25 - 30 % of light through so to compensate subs are usually longer by a factor of 3. If you can go long enough the Astronomik UHC should give a huge contrast boost but only lets through 12% of total light so sub length increases by a factor of 6.

These are single shot colour filters that let through only certain spectral lines like OIII, Hb and Ha while blocking skyglow and certain street lights.

They sometimes produce a colour shift but it's easy to balance out in Photoshop.
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Old 23-10-2012, 07:00 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Thanks for the quick reply Kevin!

That's just the sort of info I'm looking for.

Cheers,

Justin.
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Old 23-10-2012, 07:22 PM
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cometcatcher (Kevin)
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There's lots of filters to choose from and it can get confusing. I would highly recommend the Astronomik CLS for starters. It's very similar to the Lumicon Deep Sky, with just a dash more blue in the passband.

Here's a comparison between a Badder Semi-apo and Lumicon Deep Sky for the running chicken IC2944. Both are 1 hour total exposure through an ED80. The Deep Sky has some bloating of stars because it's old and has worn coatings, but still flogs no filter or the Semi-apo for Ha. I have replaced it with the Astronomik CLS which is almost identical except no star bloating.

I do have some light pollution here which may be increasing the filter effect.
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Old 23-10-2012, 07:46 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Thanks Kevin!

A big difference under light pollution, I have pretty good skies so as you say there may be less effect but still worth trying.

Cheers,

Justin.
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Old 23-10-2012, 09:44 PM
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Hi,
I also use the Astronomik CLS on my Nikon DSLR. Although I've only used it once, I found it introduced a very strange, non-linear background colour gradient. I'm expecting a light-box in a few days, so I'll be able to tell if this was the filter or the sky soon enough. It was relatively straightforward to deal with in Pixinsight, and the improvement in the image was noticeable.
cheers,
Andrew.
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Old 23-10-2012, 10:12 PM
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Hi Justin,
I'm not sure how the filters would help as you are already imaging from dark skies and you have very little light pollution.
Most of the LP filters are band pass so would reject light, but you don't have much to reject in terms of LP. so not sure how any filter would help.
I'm interested to know your thoughts though?

I can only imagine better response if you removed the factory IR filter.
As you'd know, there's the noise to contend with as you increase your exposure duration.
Cheers
Alistair
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Old 23-10-2012, 10:28 PM
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This is what inspired me to try it, despite the fact that my site is relatively dark.
http://www.astropix.com/HTML/I_ASTROP/FILTERS.HTM
the theory is that these filters do a pretty good job on the skyglow as well a the light pollution. Worked for me!
cheers,
Andrew.

Quote:
Originally Posted by alistairsam View Post
Hi Justin,
I'm not sure how the filters would help as you are already imaging from dark skies and you have very little light pollution.
Most of the LP filters are band pass so would reject light, but you don't have much to reject in terms of LP. so not sure how any filter would help.
I'm interested to know your thoughts though?

I can only imagine better response if you removed the factory IR filter.
As you'd know, there's the noise to contend with as you increase your exposure duration.
Cheers
Alistair
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  #9  
Old 23-10-2012, 10:30 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Quote:
Originally Posted by alocky View Post
Hi,
I also use the Astronomik CLS on my Nikon DSLR. Although I've only used it once, I found it introduced a very strange, non-linear background colour gradient. I'm expecting a light-box in a few days, so I'll be able to tell if this was the filter or the sky soon enough. It was relatively straightforward to deal with in Pixinsight, and the improvement in the image was noticeable.
cheers,
Andrew.
Thanks Andrew!

Something to watch out for.

Quote:
Originally Posted by alistairsam View Post
Hi Justin,
I'm not sure how the filters would help as you are already imaging from dark skies and you have very little light pollution.
Most of the LP filters are band pass so would reject light, but you don't have much to reject in terms of LP. so not sure how any filter would help.
I'm interested to know your thoughts though?

I can only imagine better response if you removed the factory IR filter.
As you'd know, there's the noise to contend with as you increase your exposure duration.
Cheers
Alistair
Your probably right Alistair, but I won't know unless I try.
Have'nt heard or seen imges taken with a CLS filter from a dark site.

Noise will increase, the orion cooler box will help although I'm not impressed with it's performace so far.
It started cooling at 15c below ambient but now is at 10C below, a long way from the up 24c below ambient touted on the orion website.
I'll be contacting BINTEL about this.
I'm not really interested in modding the camera, I'll probably cnosider a cooled CCD in the future.

Cheers,

Justin.
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Old 23-10-2012, 10:32 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Quote:
Originally Posted by alocky View Post
This is what inspired me to try it, despite the fact that my site is relatively dark.
http://www.astropix.com/HTML/I_ASTROP/FILTERS.HTM
the theory is that these filters do a pretty good job on the skyglow as well a the light pollution. Worked for me!
cheers,
Andrew.
Thanks for that link Andrew!

Cheers,

Justin.
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Old 23-10-2012, 10:34 PM
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Quote:
Originally Posted by tilbrook@rbe.ne View Post


Have'nt heard or seen imges taken with a CLS filter from a dark site.
I've got a couple on my astrobin site -
http://www.astrobin.com/users/alocky/
the M31, veil, LMC and Pleiades shots were all done with the CLS filter.
The earlier images M16, M17 M8 and M20 were done without.
cheers,
Andrew
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Old 23-10-2012, 10:36 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Quote:
Originally Posted by alocky View Post
I've got a couple on my astrobin site -
http://www.astrobin.com/users/alocky/
the M31, veil, LMC and Pleiades shots were all done with the CLS filter.
The earlier images M16, M17 M8 and M20 were done without.
cheers,
Andrew
Cheers,

I'll check them out.

Justin.
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Old 23-10-2012, 10:50 PM
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tilbrook@rbe.ne (Justin Tilbrook)
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Quote:
Originally Posted by alocky View Post
I've got a couple on my astrobin site -
http://www.astrobin.com/users/alocky/
the M31, veil, LMC and Pleiades shots were all done with the CLS filter.
The earlier images M16, M17 M8 and M20 were done without.
cheers,
Andrew
Just checked your images out.

Very impressive! It's a bit hard to judge without a side by side comparison images, but the pleiades image is possibly showing more than I got with the 8" f/4 astrograph.
Still hard to tell different setups.

Cheers,

Justin.
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Old 23-10-2012, 11:14 PM
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alocky (Andrew lockwood)
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Thanks! Must be the filter then
although, that little 4" FSQ certainly punches well above its aperture.
I've got some wide angle images I took on the same night, and that part of the sky was badly contaminated by green skyglow - so the filter did its job.

Quote:
Originally Posted by tilbrook@rbe.ne View Post
Just checked your images out.

Very impressive! It's a bit hard to judge without a side by side comparison images, but the pleiades image is possibly showing more than I got with the 8" f/4 astrograph.
Still hard to tell different setups.

Cheers,

Justin.
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