Recommendation for quark chromo pre-filter?

[skybadger]

Hi 

I'm using a quark chrome H-alpha filter on a skywatcher ST80 and I want to put a pre-filter in front to dump some of the heat. To this end I put a Baader 2" IR cut filter in the train and more or less lost the surface detail. 

Can anyone recommend a filter for this job and maybe explain why the filter had the effect it did ?

Also, my quark seems to be on-band with the knob turned to 1 o' clock when previously it was at about 6. All I did was store it indoors over the winter. Has this happened to anybody else ? Ambient is about 15 to 20 degrees in the info.

Finally, do people get better views with longer FR scopes ? This one is about f/5 and the contrast is lower than I am expecting.

Cheers

Mike

[xtreemchaos]

Hi mate, I have the same filter and it works great with my ed80, quark combo, are you sure its not just down to bad seeing . charl.

[ngwillym]

Also - with a filter in the way - I also use the Baader UV/IR - you'll probably need to retune your Quark. An alternative suggested by Rupert at Astrogrpah is to use the Baader 35nm H-Alpha filter - I've just got one of those, so I'll keep you posted on any improvement or otherwise over the UV/IR - that is of course, when I get some sunshine.

Regards

Neil

[Peter Drew]

I would prefer the Baader 35nm Ha filter, it is highly reflective which significantly reduces the heat loading on the rest of the system, if possible it should be tilted slightly to eliminate ghosting. I think there is a possibility that IR/UV filters still leak enough IR to take the edge off an image,also the residual spherical aberration of the F5 achromats has a similar effect. F6-F7 should be better. 

[skybadger]

Thanks all. I have been searching for the passband info of the filter on the baader website and can't find it. I suspect the tail off might start at 6500 or so. 

I do need to try a longer focus refractory but all I have here are Petzvals. Might assemble one once I have the time.

I shall look into the narrower passband filter too.

What do you mean by retune other than to turn the knob? Adding the filter in the way shouldn't provide any interference effect causing the passband to move that I can think off. Do you know one ?

Cheers

Mike

 

[ngwillym]

Here's the 35nm H-alpha spec:-

http://astrograph.net/epages/www_astrograph_net.sf/en_GB/?ObjectID=8186716

 

and the UV/IR one:-

http://www.baader-planetarium.com/en/baader-uvir-cut--l-filter.html

look under the specification tab - passband is 420 - 680

maybe a bit more detail in the attached doc

2459210A.pdf

[Merlin66]

I've used the Baader 35nm Ha CCD filter as a replacement for the ITF in many solar scopes. The coating and bandwidth is the same as the Baader D-ERF.

No issues, no drama.