Yup

Really impressive images Frank!

Very impressive image!

Hi there and welcome to the forum.

Your c9 is f10 already, stopping it down is going to make it closer to f20/f30, so using the TZ4 in addition would put it around f80/f120, which, is way too high. Is the c9 your only scope or do you have a smaller refractor?

Nope sorry. I'm not aware of anyone here who uses one.

Use a 0.5x reducer but reduce the spacing between it and the chip (short nosepiece on the camera), this will result in a reduction factor closer to the 0.8x you are after.

Top proms! Well done on the SPoD!

Good shot Rod! Nice surge.

Glad you had nice weather James, good report.

Nice disks there Rainer!

Great disks Alexandra!

Great images Pedro!

Top shots Stu, they came out well.

Looks good Jochen!

Good disks Terry!

Thanks for the report James. The sun is quiet apart from a few proms.

Glad you got a view in Andrew!

Nice Ha shots!

Starry Jack wrote: ↑

Sun Sep 20, 2020 2:03 pm

I had no considered putting one on the nose of the Quark.

Don't put it on the Quark nose, at least put it on the nose of the 2" diagonal, preferably well ahead of that with 2" extension tubes.

Impressive disks Dave!

Good job given the conditions Stu!

Nothing has changed as far as i'm aware. Maybe your cookies were cleared on your device? Have you had to log back into the forum recently?

I'll have to check the light cone diameter before the backplate to avoid vignetting. It's a fairly simple calculation - free aperture of the filter (mm) x focal ratio = point ahead of focal point (mm) to position the filter. You wouldn't want to use the 'absolute' free aperture, leave a bit of play...

When all the load is concentrated centrally on a 2" filter opposed to moving it higher in the light cone to use as much of the area of filter as possible the chances of wavefront error distortion is increased which then could translate as poorer image quality.

Interesting thread Raf! If I can throw something into the mix here too, sampling. Your camera has 2.4um pixels and so at 393nm (my rule of thumb, others might go for a higher multiplier) is that the pixel size x 5 should put you in the f-ratio ball park you need to be for ideal sampling. So, for the...