Filter issue!

[DJScotty]

:help::shrug::shrug::(
The previous problem of odd shaped stars has been fixed... TO A POINT.

I have 2" filters which screw on to the nose piece of my Atik 11000 camera. This then slides into the 2" adapter of the Bintel economy focuser.

Here is the issue.
When I do not have a filter in the nose piece, all is good. Lovely diffraction pikes. Everything is spot on.

When I put my Orion 2" Ha filter in the nose piece, the diffraction stars look like they have 2 comet tails on either side of them. They are pointing up.

When I put my Baader 2" OIII filter in, voilla! Beautiful diffraction spikes.

So...

There is obviously a problem with the Ha filter SOMEWHERE! Can anyone explain what it could be?

Cheers!
DJ Scotty

[gregbradley]

I think you are just looking at variatiions in quality unless someone is using the Orion and getting good results.

Greg.

[Slawomir]

Hi Scott,

Could it be caused by filter not being orthogonal to the optical axis? Maybe try unscrewing the filter a quarter turn and then take a test image without changing camera's orientation?

I hope you will quickly rectify the problem.

[ZeroID]

A big smear mark on the filter ?
Can you post a pic of the effect ?

[DJScotty]

Hi Brent, the Ha filter is very clean. And it has in the past produced very good images...

Which takes me to Greg and Slawomir's suggestions.

The thing I don't get is that this is the same filter I used on the ED80, with beautiful results. I am screwing the filter into the same nose piece. The only difference is that the female end of the filter, when used on the ED80, would screw into the 0.85 focal reducer/corrector for the ED80. With the 10" newtonian, it is slipping into the focusing tube. So instead of being held in place by the thread, the nose piece is taking all the weight, being held by the compression clamp of the focusing tube...

I have to say, the Orion filter is notoriously difficult to screw in, whereas the Baader filters screw on quite easily. The physical differences between the Baader and the Orion filters are about a 1-1.5mm difference in diameter (with the Orion filter being bigger) but is still smaller than the nose piece diameter. So could it be the Orion filter is somehow pressing against the inside surface of the focusing tube causing the camera sensor to be unorthogonal (is that a word?!)

Thank you for your suggestions gentlemen. Appreciate your help...

[Slawomir]

That could be an excellent excuse for getting Astrodon 3nm Halpha filter...pricey, but IMHO, it is at least equally as important as a good camera or a quality scope, in particular when shooting from suburbs :)

[DJScotty]

Hey Slawomir

I tried your suggestion with no tension at all on the filter and there was no difference. Still producing very odd shaped images.

I am imaging tonight with the OIII Baader filter in. Beautiful imaging!

SO...

That sounds like a cunning plan my good man...

So you would go Astrodon over Baader? And when you say PRICEY, what are we looking at and from where does one acquire such a filter?

Thanks Slawomir :thumbsup:

[ZeroID]

Is the filter ring being compressed, distorting the filter itself by being a tight fit, possibly pinched and stressed ?
Anyway to just secure the filter in place without threading it on ? Even if it's not perfectly parallel it might at least prove or disprove the cause.

[Slawomir]

Sorry to hear that the filter still does not work properly.

As for your question- Astrodon all the way. I bought mine directly from the manufacturer, just google "Astrodon filters". Was previously using Astronomik 12nm filters, they are very good, but not nearly as effective in increasing S/N ratio as 3nm from Astrodon.

P.S. Have you considered acquiring an electric filter wheel? I know...the plan is getting better and better...

[DJScotty]

Well, it is definitely the Orion Ha filter.

Don't know what has happened to it. But I attached it to the ED80 last night. Very distorted star images coming through. Put the Baader filter in, perfect imaging.

It's funny. The Orion filter was working fine not 2 weeks ago. Maybe the 2yo or the 3yo got their hands on it or something... But it is stuffed...

Hey does anyone want to buy a used Orion ha filter?! ;)

[Slawomir]

Hi Scott,
You have just discovered an effective way of 'disposing' of old equipment to justify buying new gadgets for astrophotography... ;)

[astro_nutt]

Hi Scott.
I'm not an expert in the use of filters but I have had my fair share of problems.
Just a question, does the tails of the star images always happen in the same place on the image?
Could it be the filter glass itself is loose/not seated properly in it's retainer?
Could it be the filter not seated squarely?
I hope this helps!
Cheers1

[DJScotty]

The filter glass does rattle inside the housing. Have had to use lots of brute force and inappropriate tools to unscrew it from the ED80 on various occasions in the past... :mad2:

[Slawomir]

Might be worth considering getting an electric filter wheel to protect your filters (and the camera!) from potential damage; once you place filters on a wheel you never need to touch them again and your optical train is nicely protected from dust.

I think screwing filters onto the nosepiece for each session will eventually lead to damaging the filters, be it by an accident or mechanical wear...

A drop of WD-40 on the threads before assembling parts of the optical train can be useful too :)

Just my two cents...:thumbsup: