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Old 30-05-2020, 09:02 PM
RyanJones
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Originally Posted by Merlin66 View Post
Ryan,Thanksk for the feedback....
Did you test it against a UV-IR filter??
Hi Ken,

Not as yet. I’ve been meaning to order it but I just haven’t gotten around to it yet. I ordered an OAG at the same time and I’ve had secondary dew issues to contend with which have drawn my attention to building a dew heater system. I might jump online now and see if they’re in stock and order it now. The post has been pretty slow of late so it should give me some time to deal with the other issues before it arrives.

Cheers

Ryan

Edit: it’s on back order

Last edited by RyanJones; 30-05-2020 at 09:13 PM.
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  #22  
Old 30-05-2020, 09:23 PM
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gregbradley
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Autoguiding programs calculate the centroid of the star so whether they are sharp or not may not be so important. I do find though that if I start an autoguiding sequence the first thing I do is select another star. Especially one that is a bit less bright and tighter. It usually works and I get a significant improvement.

I have used a 720nm IR filter on my guide cam before. I haven't used it in a while.

As I recall it did help somewhat but it also dropped the luminance of the guide stars a lot so it was really only practical when you had a bright guide star which you can't always get. M104 for example has hardly any guide stars near it.

So unless you are prepared to remove it and put it back on depending on the guide star availability its probably not worth it.

You'll get a bigger gain by doing a more perfect polar alignment with T-Point.

Also I believe you raise aggressiveness of guiding when the seeing is good not when its poor. If seeing is poor you end up chasing the seeing and overcorrect. When the seeing is good you can correct more aggressively without chasing the seeing and overcorrecting.

On my high quality mounts (Software Bisque PME and AP1600) I use 6 second guide exposures. When I had a Tak NJP mount I used 1 second. 6 seconds works better as the corrections don't overcorrect as the mounts periodic error is low. Of course that will vary with the mount but I think its most likely the weaker the mount the shorter the guide camera exposure time.

Greg.
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  #23  
Old 31-05-2020, 09:02 AM
RyanJones
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Hi Greg,

Thank you for your input. Very interesting. Can you explain what PA with a T point is ? I use the PA sequence in my ASIair. It tends to get me within a couple of dozen arc seconds. I find that the Dec is pretty good at under 0.5 RMS which I would imagine suggests that the PA is “ good “ relatively speaking. I am interested is what the T point is though. To be honest I’m not expecting miracles from testing the different filters, I just find it interesting. I image in Bortle 8 skies and my seeing is never “ good “ so I’m working with a pretty bad canvas to start with.

Cheers

Ryan
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