105mm CFF telescope has arrived! - Page 3

LewisM · #41 25-04-2017, 08:27 AM

Quote:

Originally Posted by gregbradley

If AP contacted me and said they had a 130GTX ready I would go for it.

Greg.

There is an as-new 130GTX on the 2nd page of the ice trades...

Slawomir (Suavi) · #42 25-04-2017, 06:57 PM

Well, I thought of testing the CFF flattener as well.

Link to a star field: http://www.astrobin.com/full/293190/0/?nc=Slawomir

Now have a dilemma, image with the flattener or with the Riccardi reducer...

Atmos (Colin) · #43 25-04-2017, 07:10 PM

I think your biggest issue is tilt. At F/5 I was finding that anything more than 0.1mm tilt would be noticeable in the corners. With your reducer you're getting more than that AND shooting at F/4.5.

With the flattener you're getting a bit of tilt with quite small pixels which can exaggerate the issue.

Slawomir (Suavi) · #44 25-04-2017, 07:19 PM

Thank you Colin for your advice.

I used to think that unlike big sensors, a small CCD like ICX814 is easy for imaging and more forgiving in terms of perfect alignment. Well, tiny pixels highlight any misalignments very well!

After recent investigations I realised that I may need to move the Riccardi reducer in by about 1-2mm to flatten the field. I agree, there is a tilt with both units and Catalin very kindly offered to make an adjustable adapter that will help me to tune in spacing and tilt. Also, moving the flattener in by 1mm will make the field even flatter.

Slawomir (Suavi) · #45 30-04-2017, 11:21 AM

I would like to conclude this thread with the following confession: in the past years I owned several pieces of astro equipment. I still vividly remember excitement of unpacking and using my first telescope. It was Saxon - a 6" f/8 Newtonian on non-motorised EQ3. Had many many memorable nights of stargazing with it from our balcony in Rockdale in Sydney, and also dipped my feet into astrophotography with this telescope. I had a few more telescopes since, but looking through and using the CFF 105 revived that special astro-thrill I had with my first telescope back in the days.

Slawomir (Suavi) · #46 30-07-2017, 03:44 PM

Sorry to resurrect this old thread...

Since I have finished collecting data for my latest image of the Prawn, I decided to fine-tune camera's orthogonality (I have a camera tilting unit from Gerd Neumann).

I think I got it pretty close to perfect, perhaps I could move the camera 0.5-1mm further out, but nonetheless I am now very happy with star shapes: http://cdn.astrobin.com/images/thumb...20Lipinski.jpg

I had a chance to use this telescope on about 30 sessions since I've got it. Love the mechanics and optics. Machined tube, machined baffles, FTF 3.2" is rock solid and autofocus is very precise, oil-spaced lens cell seems to cool fast. Refocus is needed perhaps every 1.5-2.0 C change if you are after perfect focus. When changing filters, there is hardly any adjustment needed. I think this scope would be a very nice match for KAF16200 for wide fields, one day perhaps.

Suavi

gregbradley · #47 31-07-2017, 10:56 AM

Oh wow, that is spot on. I don't think I have ever seen a plot that good. Nice one.

But the proof is in 1x1 binned exposures and checking each corner for star roundness perfection not really CCD Inspector which can sometimes give 2 results for the same image.

16200 would go well with it. Can it handle a 16803 with its 52mm diagonal? 16200 has a 44mm diagonal from memory. .5 to 1mm is a very large correction by the way.

Greg.

Slawomir (Suavi) · #48 31-07-2017, 11:47 AM

Thank you Greg. It took a few iterations to get it right. I won't be adjusting the spacing at this stage, but CCD Inspector consistently indicates that my CFF corrector slightly overcorrects field curvature at the current spacing, so that is why I think I may be a tiny bit off the perfect spacing.

Stars are nicely round though to my eye in the recent test image; it would be silly if I complained about current star shapes

I would be VERY happy to test either KAF 16200 or KAF 16803, just need to find a donor, or perhaps if things go well, I just wait patiently a few years for a Santa to accumulate sufficient funds

Atmos (Colin) · #49 31-07-2017, 11:59 AM

That looks very nice Suavi!! That over correction you mention, that may be what it is designed to do. There is always going to be some level of field curvature.

The 16200 has a diagonal closer to 35mm being an APS-H. A full frame is ~43mm.

Slawomir (Suavi) · #50 31-07-2017, 01:01 PM

Thank you clarifying that Colin. I have been assured that this scope is fully corrected to 44mm for imaging with my flattener, and with 3.2inch focuser it should do well with larger chips.