qhy8 and mpcc - screwed up again...

[uhb1966]

Oh boy...

Just found out that last nights photos are for the bin... didnt realize that a coma corrector has to sit in a well-defined distance to the ccd plane to work... which in case of the baader mpcc is 55 millimeters. Silly me. This hobby is driving me nuts!!!

In my defense, the mpcc comes out of the box with the more or less right spacing for my canon eos 550d, so i never had to worry... until i tried to mount it to my new used qhy8!

[MattJenko]

welcome to spacer hell

[uhb1966]

Thank you Matt, very much appreciated! 

re master of none: "So it is good, so it is right: no one's master, no one's servant"  -Beethoven 

 

[Shelster1973]

Am one of the people wearing this t-shirt too.  Fell foul after moving from my D7100 to the SXVR-H694.

Also went one tweak to far and broke out the calipers thinking i could get that sorted, but looks like I may have added too many spacers.  Tweaked back and now waiting to test.  Have fingers crossed on this one.

Would be so much easier if ccd and coma corrector manufacturers placed marks on the outsied of the body so that you know where the essential parts to measure between are......

[Waldemar]

8 hours ago, Shelster1973 said:

Am one of the people wearing this t-shirt too.  Fell foul after moving from my D7100 to the SXVR-H694.

Also went one tweak to far and broke out the calipers thinking i could get that sorted, but looks like I may have added too many spacers.  Tweaked back and now waiting to test.  Have fingers crossed on this one.

Would be so much easier if ccd and coma corrector manufacturers placed marks on the outsied of the body so that you know where the essential parts to measure between are......

In the information sheet that is deliverd with the CCD camera as well as the correctors, the backfocus is allways mentioned.
If the corrector info says 56 mm (more or less standard) that means that the distance to the sensor should be 56 mm
If  the camera info says 20 mm, that means the distance from the edge of housing (beginning of the thread at the sensor side) to the sensor is 20 mm.
So: 56 -20 is 36 mm to be filled in with spacers. The Baader Varilock ( http://www.baader-planetarium.com/de/zubehoer/adapter-foto-zubehoer/astro-t-2-system/varilock-46-arretierbare-t-2-verlängerungshülse-mit-spannschlüssel-(t-2-bauteil-25v).html )
can be adjusted from 29-46 mm, so you can always find focus with almost any CCD camera. There is a shorter one as well from 20-29 mm. The both cover all thinkable backfocus distances you may ever need.
Of course there are also plenty options for fixed spacers, but these Varilocks are very practical and allow you to find the perfect distance.