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Old 17-09-2011, 11:46 PM
DJ N
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First Light - Hotech SCA Field Flattener

Hi everyone,

This week I received my Hotech SCA Field Flattener. I was very surprised to how compact it is, especially when compared to my William Optics P-Flat IV. I decided on giving the Hotech a shot, as I was really after a flattener that would not reduce the focal length on my ED120. This Hotech fits the bill from that perspective. It is designed for f5 to f8 telescopes.

The other interesting feature is the self centering. Once you slide the flattener into the 2 Inch focuser on the scope, you just tighten the adjuster on the flattener. As you tighten it, 3 rubber rings press against the focuser ensuring a central fit. Technically you do not need to worry about the compression ring/screws on the focuser itself. However, being paranoid, I did tighten the focuser compression ring ever so slightly.

According to the manufacturers specification, a distance of 55mm is required from the CCD face to the flattener. With the QHY8L, I needed to make up 32mm, however I could only get 30mm with the spacers I have at the moment. I do have the appropriate spacers on order, so hopefully my next test will be done at the proper spacing.

Anyhow, pretty happy with the initial results. I have tried the flattener with both the ED120 and the ED80 and things are looking very promising.

Looks like I might put the WO PFlat 4 onto the classifieds!!

Anyhow, here are the intial results from tonight;

Image 1 : M8 and M20 with the ED80 and the Hotech SCA Flattener, imaged with the QHY8L (4 x 8 minutes)

Image 2 : M20 with the ED120 and flattener, imaged with the QHY8L (3 x 10 minutes)

Cheers,

Daniel
Attached Thumbnails
Click for full-size image (M8 and M20 17Sep11 ED80 QHY8L 4x8m  Hotech Flat 30mm Post.jpg)
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Click for full-size image (M20 17Sep11 ED120 QHY8L 3x10m  Hotech Flat 30mm Post.jpg)
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Old 18-09-2011, 12:50 AM
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atalas
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Daniel,the SCA is very interesting...can you put up a larger image cause It's hard to tell at this scale how well It works.

Hm,creating a flattener for multiple focal lengths seems like there would have to be a compromise somewhere, but still I would like to get a look at a large image before arriving at any conclusions.

Hey,by the way a couple of nice shots there.
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Old 18-09-2011, 02:46 PM
DJ N
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Not sure how to attach larger images, but I thought I would at least add some shots of the corners of the images.

First up, the ED80

i. Top LH
ii. Top RH
iii. Bottom LH
iv. Bottom RH
v. Centre


Cheers,

Daniel
Attached Thumbnails
Click for full-size image (ED80 Top LH.jpg)
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Click for full-size image (ED80 Top RH.jpg)
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Click for full-size image (ED80 Bottom LH.jpg)
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Click for full-size image (ED80 Bottom RH.jpg)
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Click for full-size image (ED80 Centre.jpg)
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Old 18-09-2011, 02:48 PM
DJ N
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And the the ED120

i. Top LH
ii. Top RH
iii. Bottom LH
iv. Bottom RH
v. Centre


Cheers,

Daniel
Attached Thumbnails
Click for full-size image (ED120 Top LH.jpg)
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Click for full-size image (ED120 Top RH.jpg)
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Click for full-size image (ED120 Bottom LH.jpg)
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Click for full-size image (ED120 Bottom RH.jpg)
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Click for full-size image (ED120 Centre.jpg)
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Old 18-09-2011, 02:53 PM
DJ N
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For comparative purposes, here is the top LH with the ED120 with no flattener and one with the flattener.......
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Old 18-09-2011, 05:03 PM
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Very good results Daniel....flatter than a BabyQ!
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Old 18-09-2011, 07:41 PM
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That's a very good improvement but there is still some coma showing. Perhaps the spacing is not ideal yet. I am being picky.

Greg.
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Old 18-09-2011, 08:04 PM
DJ N
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Quote:
Originally Posted by gregbradley View Post
That's a very good improvement but there is still some coma showing. Perhaps the spacing is not ideal yet. I am being picky.

Greg.

I am just waiting for the approriate spacer to arrive. At the moment I am 2 mm short per the specified 55mm spacing from the chip to the flattener. Hopefully once I get the correct distance, there will be a slight improvement.

Cheers

Daniel
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