New Scope

[jimwc6491]

I just bought a OPT/TPO 8" F/8 RC. looks like I might be able to get first light this evening.

any Idea of what ISO, shutter speed, and duration is a good starting point.

 

I know I will have to guide with this scope. where it was optional with my F/4 Newt. as the duration will be in the multiple minutes rather than <90 seconds with the Newt.   

[s3igell]

The Extension Tubes - did they come with the TPO RC??  If so, these are the 90mm Dia. Screw-ON type which DEFINITELY go between the Rear Cell and the Focuser.

 

The Collimation Ring ALSO goes between the Rear Cell and the Focuser - probably should go between the Rear Cell and the 1st Extension Tube since the Collimation Screws would be hidden by the Front Flange of the Focuser if it were put between the Last Extension Tube and the Focuser.

[astroman133]

Once the moon sets, I would start with 6 minutes at ISO 800, and adjust based on the histogram.

 

Good luck with collimation. RC's are finicky to collimate. A good collimation tool and some practice are essential.

[jimwc6491]

Rick

Thanks. I already plan to get the hotech RC culmination tool if it looks too bad with the star test.

I had to get a couple adapters already, one for the mount and one for my focuser.

other than that everything seems to be fitting together pretty good. tonight will tell.

[astroman133]

Have fun!

[jimwc6491]

Rick

How does this look for collimation?

it appears a little off to me what do you think.

[astroman133]

I agree. It may take some practice, but it can be improved.

[admin]

This is still off but you are close.

[jimwc6491]

its not bad for being almost right out of the box.

I have had it on the mount a couple of times during the day.

this was first light.

[jimwc6491]

Guylain, Rick, or anyone knowlegable.

I bought a collmation ring to collminate the focuser do I put it between the scope and extension tubes, or between the extension tubes and the focuser?

[astroman133]

Jim,

 

What kind of collimation ring? Is it for your RC? If so, I would think that it would go between the rear cell of the RC and the focuser. However, I do not believe that one is normally necessary unless you have a full-sized sensor. That said, if properly installed it shouldn't hurt. Extension tubes would typically go right behind the focuser. and then the rest of the optics (focal reducer and camera). If you are not sure you could call OPT for confirmation.

[jimwc6491]

Rick

yes it is for My RC. the OPT Item # is os-fcr-rc6-8. I have had to put 4" of extension tubes in order to get focused.

these extension tubes screw right on to the rear cell I am using 2-1" and 1-2" then the focuser adapter and focuser.

I was wondering if that could be the reason I'm out of collimation possibly a little droop.

I was just wondering if I should put the collimation Ring on the rear cell, or on the extension tube between the tube and focuser, or does it matter.

[astroman133]

I would check with OPT. The extensions are empty tubes so it should not matter which side of the focuser they are on, but putting them in front does not seem the way to go.

[admin]

You usually put those in front or behind the focuser, before the extensions.  The most important criteria is collimation screw access IMO.  If you can't reach them it is not useful.

[s3igell]

And, looking at the OP Image, I'd say the Collimation Issue is still with the Secondary Mirror Cell.

I once had to address the same Issue with my GSO RC6 (original source of the TPO Branded RC6).

[jimwc6491]

s3igel

Thanks.

yes the Extension Tubes are the ones that came with the scope.

I put the Cullimation ring between the rear cell and the first extension ring

then realized that it could go between the last extension ring and the focuser,

I thought I should ask so I got it right.

Thanks again