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new reducer/flattener from Astronomics...

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#26 Aboy

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Posted 29 October 2012 - 12:55 AM

them is better to buy the TV one after all? :confused:

#27 Midnight Dan

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Posted 29 October 2012 - 06:41 AM

I have a question about this reducer..

I waiting for my TV pronto in the mail.. this reducer its ok to use in the TV pronto?


Hi Aboy:

Your TV pronto is F/6. If you read the information on the Astronomic website for the reducer/flattener, you'll see that it is rated to work with f/5.5 to f/7. Based on that, it should work.

-Dan

#28 nemo129

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Posted 29 October 2012 - 10:36 AM

Some brands have reducer/flattener specifically for their scopes, this is a plus as you get matched results without worry.



Just my .02 and observation. I agree with Jim's opinion above. TV has tested the Pronto and the TRF2008. It should work without issue. Not that the new AT unit will not, but for $145 more you know you will be getting nice stars in all the corners..that would be worth it to me. You may be spending hundreds of hours taking pictures..nice to know you will not have to wrestle with spacing issues to get good stars. That was my .02. The observation is TV makes top shelf gear and I have never had a quality issue with it. I have had issues with machining and optical component alignment on "other" brands. Not to say all of them have it or will have issues, but you do get what you pay for and it is nice to only pay once!

#29 CounterWeight

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Posted 31 October 2012 - 04:17 PM

-update,
It still has not cleared long enough for even a rough focusing check. :( All I need is maybe 10 minutes of clear sky - all set up and ready to go when it finally does.

#30 ad701xx

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Posted 31 October 2012 - 11:32 PM

Hopefully we'll get a little break in the weather on Friday. I'm not holding my breath, though.

#31 SMigol

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Posted 04 November 2012 - 01:50 AM

Finally got out under the stars for some testing of this device with my SV4 (APO 102mm at F 5.71 for 581 mm FL by platesolve).

Ran it against the Pleiades for a quick and dirty test on my Pentax K10D camera.

Here's how the results look at 43 seconds:
Posted Image
Testing Astronomics Reducer Flattener by S Migol, on Flickr

Go here for a bigger view: http://www.flickr.co...tream/lightbox/

Here are the platesolve results from PixInsight:
Iteration 3, delta = 0.013 arcsec (0.0 pixels)
Image center ...... RA: 03 46 28.591  Dec: +24 01 00.27
Resolution ........ 2.39 arcsec/pix
*****

Image Plate Solver script version 1.51
===============================================================================
Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):
        +0.000125873835     +0.000650703735     -1.096325533721
        -0.000650629315     +0.000125836022     +1.102834553734
        +0.000000000000     +0.000000000000     +1.000000000000
Resolution ........ 2.386 arcsec/pix
Rotation .......... -100.950 deg
Focal ............. 466.86 mm
Pixel size ........ 5.40 um
Field of view ..... 2d 34' 55.1" x 1d 44' 1.3"
Image center ...... RA: 03 46 28.591  Dec: +24 01 00.27
Image bounds:
   top-left ....... RA: 03 41 38.086  Dec: +25 06 52.28
   top-right ...... RA: 03 43 51.148  Dec: +22 35 01.28
   bottom-left .... RA: 03 49 09.579  Dec: +25 26 48.98
   bottom-right ... RA: 03 51 14.155  Dec: +22 54 34.61


The CCDInspector shows interesting results as well:
Posted Image
SV4 with Astronomics Reducer Flattener Curvature Map by S Migol, on Flickr

Posted Image
SV4 with Astronomics Reducer Flattener Curvature 3D Map by S Migol, on Flickr

#32 Phil Hosey

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Posted 04 November 2012 - 07:17 AM

The stars on the left side are quite distorted. Even the bottom-right is distored although not quite as much. This looks a lot like what I get with a William Optics Reducer/Flattener II.

#33 SMigol

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Posted 04 November 2012 - 01:00 PM

I've used the WO and get much worse stars. I'm starting to add spacers and it's responding nicely so far. With .5 mm spacer added, the curvature improved 1% and the stars got a little tighter. Will keep working it tonight and see how it improves.

#34 Phil Hosey

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Posted 04 November 2012 - 01:55 PM

I'll be interested to see how it goes. I currently use the William Optics AFR-IV reducer/flattener which corrects the stars very well, but unfortunately it causes reflections on bright stars. I'm very interested to see how the Astrotech reducer performs.

#35 CounterWeight

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Posted 04 November 2012 - 03:59 PM

SMigol - what is your spacing that are starting with? is your imaging trane 'all threaded'?

#36 Mike7Mak

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Posted 04 November 2012 - 04:59 PM

With .5 mm spacer added...


Is that correct? That's about the thickness of a fingernail.

#37 SMigol

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Posted 04 November 2012 - 05:01 PM

I haven't measured the spacing "vanilla." Here's what it's supposed to be by common standards:
Pentax K mount flange distance: 45.46 mm
K mount to T thread adapter: 10 mm

This camera has been full spectrum modified, I've computed the glass thickness as 1.4 mm based on reflections of bright stars.

Given the usual rule of thumb about glass adding 33% of its thickness to the optical train for backfocus, then I should be adding .46 mm.

By these numbers, I should be trying to remove about .9 mm of backfocus to bring it to the proper setting. However, when I added the .5 mm spacer, the flatness went down by 1% and the star images improves, it leads me to think that there are other factors in play.

I should measure the actual flange distance of the camera. I've had disagreement with a ronchi screen set to proper distance so there may be issues with this camera from the factory.

Nearly all the devices are threaded. The only two parts that are not threaded is the reducer/flattener to the feathertouch focuser and the camera mount is a flange device. I've wrapped that flange with teflon tape to tighten it up a little, as well. I do have a way to support the camera so that there is no weight resting on the focuser. I will do that as a part of my full testing once I get proper spacing. That will be the exercise to center the camera and get it flat.


EDIT: the .5 mm thickness is correct, I'm using brass rings from Edmund Optics for tweaking. I have a .5, 1, and 1.5 available. I also have some screw on spacers that start at 5 mm.

Second Edit:
I've measured my camera setup and here's what the values are:
Camera flange distance to the glass: 46.91 mm
T Ring thickness is 9.3 mm

My stock non-converted camera has a flange distance to the front surface of the IR filter of 47.2, so this seems to make sense.

#38 SMigol

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Posted 05 November 2012 - 03:45 AM

I ran through a battery of tests this evening, using spaces from 6 mm through 2 mm and a baseline again of no spacers.

I think that some of my numbers from the previous night were misleading. By going through the whole set again under one night and matching the practice carefully, I can see that spacers don't effect flatness. While this should not be a surprise, I wasn't sure what to expect.

So it appears that the flatness of this device does not work well for my SV4. It may work well for other scopes in my setup, including the SV 70 ED and the ST 80. I'll have to try these out.

In the meantime, I'll keep using the flattener that I have that gives very nice stars across the field and work on mosaics.

#39 Midnight Dan

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Posted 05 November 2012 - 07:21 AM

In the meantime, I'll keep using the flattener that I have that gives very nice stars across the field and work on mosaics.


Which one is that?
-Dan

#40 CounterWeight

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Posted 05 November 2012 - 10:13 AM

I was able to do a rough focus check finally (coming in from too close/too far)- but nothing qualitative, shooting through rapidly moving holes in the clouds/high haze with 3 sec bin*2 exposures. 'Desperation imaging'. No issues with in/out focus and I think critical focus will be near where I found it using the TRF. Having done this will make it that much easier when the weather clears.

#41 SMigol

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Posted 05 November 2012 - 10:52 AM

In the meantime, I'll keep using the flattener that I have that gives very nice stars across the field and work on mosaics.


Which one is that?
-Dan



I've been using the Stellarvue one for F6 scopes. It looks like the old AstroTech flattener, but there are no identifying markings on it.

While I'd like to get more of a field of view via a reducer, I'm going to run the numbers on this SV flattener and see what the extrapolated curves would be if it had a slightly larger field of view. Might be that this Astronomics reducer flattener is doing exactly what it's supposed to be doing!

#42 CounterWeight

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Posted 05 November 2012 - 10:25 PM

Well I am getting some photons - we'll see if it lasts? Not a great night but should be ok for point sources?

#43 CounterWeight

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Posted 06 November 2012 - 12:05 AM

Ok...
here is a single 10 minte sub using the Baader 7nm Ha+[NII] filter LINK

and here is a link to a full sized FITS version. LINK for those that want to download and inspect at full size.

Nothing done to these, no claibration or anything. Was only able to get three 10 minute images before clouded over.

Hope these help move the evaluation forward.

Attached Files








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