Time Flex

[LucMurphy]

As anyone had experience making a diagnosis of flexure with the Sequence time flex tool?

 

I am trying to do so by making time flex measurements in different part of the sky (incuding pointing to the zenith) hoping it would give me a clue what needs to improve in my imaging train. The first thing i noticed however is that sequence gives me a much shorter unguided time than what i can actually acheive. Sequence gives me a fairly consistent 8-10 arcsec over 20 min time flex (for sequence that's an equivalent of 1-2 min unguided with 1" error) while i can achieve consistent 5 min unguided subs (10 min unguided however is a challenge)

 

Before anyone ask, my setup is:

DDM60

Celestron edgdhd 11" (with miror locks)

Moonlite focuser (I have order from Moonlite a special drawtube, so i am confident that the filter wheel to focuser connection is rigid and i have not notice any slip)

FLI filter wheel

FLI MicroLine

Total payload 21-22kg

 

The pointing file is excellent and Autoslew says I'm .5'/1.5' from the pole. I have a permanent setup.

 

Any ideas?

 

Thanks

 

Luc

 

[P.Keller]

you will probably notice, that the most error of the 10 arc sec happens in the first part of the flex time.

This is something that will help you in real exposures.

Also if you have 1.5" trailing and you have 2" seeing the image will not look so bad.

Have you ever measured the real trailing by making short 5s exposures every minute and then determine the pixel localtion of a certain star ?

Your result is not unusual. You can be sure the result is real because the mount stays exactly in place and always slews back to the same encoder reading, removing any pointing error the mount could make. Therefore, also polar alignment is completely irrelevant in this test.

Maybe you cannot optimize this with a SC telescope. I am not experienced with them.

[LucMurphy]

Thanks Philip,

 

Yes, i have already notice that flex occurs mostly in the first few minutes, but not always, I've made 2-3 flex measurements with very steady drift (scope was point to the zenith). To be sure however, I have actually taken the habit of adding a 2 minutes delay after the end of the MLPT run before starting an exposure sequence.

 

Not sure what you mean by:

"Have you ever measured the real trailing by making short 5s exposures every minute and then determine the pixel localtion of a certain star ?"

I have bieng using the time flex measurement in Sequence. Or are you talking about something else?

 

I know SC are inherently more difficult to make more rigid but i still hopeful. I will start making measurement with my Canon to see if the weight of FLI MicroLine+CFW could be the source of the flexure.

 

Thanks again

Luc