Jupiter May 13 845AEST

[matt]

Sorry guys.

Just wanna make one point clear. When I said I don't understand the positive/negative projection thing, that wasn't a slight on you in any way Paul. Just meant I don't understand how it works.

More research for moi

Now, here's a question. I understand the perils of collimating a SCT with a diagonal in place if I'm not going to use a diag when I'm imaging.

But when I have been collimating my scope I've been doing so by eye with the ep straight in the visual back. No barlow ... no Powermate.

But when I image, I use a powermate.

Sooooooo ... could that be contributing to any type of collimation error????

Should I be collimating with the barlow or powermate in place, if that's the optical train I'm using when I capture???

Or does that not present the same mis-collimation issue as a diagonal??? the

[[1ponders] (Paul)]

This Excel sheet may give you an idea of what you can do with Extended Eyepiece Projection (another name for positive eyepiece projection)

It is made up of two pages. You only need to fill information on your scope and eyepieces on the first page onlyThe first page is for afocal photography but the various parameters are linked onto the second worksheet.

For EEP all you need to do is fill in your Telescope FL, your various eyepiece FL and your telescope objective (towards the bottom of the worksheet) on the first worksheet. If you are interested in the afocal option you can also fill in the camera lense FLs as well. Just delete any existing eyepieces and camera lens FLs.

If you then go to the second worksheet the top table will give you the various magnifications of the system (apply this magnification to the "normal" magnification of the system ie 1000 mm FL with a 20mm eyepiece gives 50 X. Multiply this 50 X by the magnification factor from the top table.)

The second table will give you your effective focal lengths based on how far the chip is from the eyepiece

And the third table give you your f/ratios at the various chip distances and eyepieces.

If you have any problems give me a yell.

BTW the grey areas on each table are where the most useful ranges are. This will probably be incorrect as I initially set the work book up to use with an SLR camera.

[[1ponders] (Paul)]

None taken

I would hope that there isn't a problem with a powermate. Not at those prices. It's mainly the diagonal

[Dennis]

Originally Posted by matt

Sorry guys.
>snip
Should I be collimating with the barlow or powermate in place, if that's the optical train I'm using when I capture???

Hi Matt

I have always collimated with the x2.5 Powermate in place, using a 20mm Plossl (medium magnification x235) followed by a 9mm Vixen Lanthanum (x522) and then I remove the eyepiece and plug in the ToUcam and eyeball the inside and outside focus position on the notebook display and it looks the same as looking directly through the 'scope.

From memory, my experience has been that although I check every 4 to 6 weeks, I have only tweaked it once originally, followed by two minor tweaks in the 4 or 5 months I have been collimating.

Cheers

Dennis

[matt]

Great. Thanks Dennis.

And all you guys for your help and encouragement.

Well, I'm all set up and have been since 5pm. Scope nicely chilled. Did a quick check of collimation in the 10mm XW and it looked sweet.

Even with a 5mm in the back (470x) the rings are concentric and the airy disc is centred.

Just had a quick look at jupiter with the 10mm XW (235) and the detail is very encouraging. Swirls, knots, festoons... the works! I'd put the seeing around 6/10 and getting better. Even the jetsream map looks good, not that that's proven a winner of a form guide lately

So I'm getting right back in the saddle, digging the spurs in, and taking this pony for another ride

See you when the mud dries. Yeeeehaaaa!!!!!!!