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Esprit 120 flattener spacing

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10 replies to this topic

#1 leemr

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Posted 09 June 2016 - 05:34 PM

I've seen several figures for correct spacing of this flattener. Is anyone able to confirm, based on experience, what has actually worked?


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#2 leemr

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Posted 10 June 2016 - 07:47 PM

Anyone? I'm going to need to order some precise parts adapters, which will cost me about $432AUD to land... don't really want to mess that up.


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#3 ericsolo

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Posted 11 June 2016 - 12:50 AM

Check the Skywatcher Esprit 120 User Manual, page 8. 

 

http://skywatcherusa.../support-center

 

Eric



#4 leemr

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Posted 11 June 2016 - 01:10 AM

Thanks Eric, appreciate the response.

 

I'm not sure if the information in the manual is correct, thus why I posted this thread. First of all, the markings on page 8 differ to those on page 9. Secondly, a Skywatcher rep told someone in this thread that the spacing should be 69.8mm from the metal cell. The rep went on to say that the number in the manual is from the lens element itself, but the document clearly says otherwise.

 

It's probable that the rep is correct, but I just wanted to hear from someone who'd successfully used the flattener to be sure that was the case before forking out a big chunk of cash on adapters.


Edited by leemr, 11 June 2016 - 01:11 AM.


#5 ericsolo

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Posted 11 June 2016 - 12:47 PM

Interesting.. I checked the Canadian Skywatcher manual, and it is the same.  I have an Esprit 150, and page 8 and 9 of the manual provides two distances, 100mm from the front of the ring with the writing on it, and 96mm from the back of the ring.  Have a look at this link and you will see what I mean:

 

http://skywatcher.co...01416868668.pdf

 

This suggests to me that perhaps Skywatcher updated the 150mm manual, but forgot to update the 120mm manual(or made and error).

 

My best advice would be to contact Skywatcher directly.

 

Eric



#6 Adam E

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Posted 11 June 2016 - 01:04 PM

I think I would try the flattener for myself and determine the correct spacing first hand before investing in a Precise Parts adapter.  Your own spacing may vary from any manual spec and/or other user depending on whether you have a filter and so forth in your imaging train.



#7 Orion58

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Posted 12 June 2016 - 09:21 AM

I've seen several figures for correct spacing of this flattener. Is anyone able to confirm, based on experience, what has actually worked?

 

I would suggest emailing Kevin at Skywatcher to get a clarification:  klegore@skywatcherusa.com

 

Kevin is very helpful.



#8 leemr

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Posted 14 June 2016 - 02:01 AM

Interesting.. I checked the Canadian Skywatcher manual, and it is the same.  I have an Esprit 150, and page 8 and 9 of the manual provides two distances, 100mm from the front of the ring with the writing on it, and 96mm from the back of the ring.  Have a look at this link and you will see what I mean:

 

http://skywatcher.co...01416868668.pdf

 

This suggests to me that perhaps Skywatcher updated the 150mm manual, but forgot to update the 120mm manual(or made and error).

 

My best advice would be to contact Skywatcher directly.

 

Eric

 

Ahh, that's very interesting. I think you might be right. I recalled a thread where a guy who'd bought an Esprit was livid after being given the wrong information by Skywatcher and then buying an expensive custom adapter from precise parts that was inappropriate. May be that they corrected the 150's but not the 120's manual.

 

 

I think I would try the flattener for myself and determine the correct spacing first hand before investing in a Precise Parts adapter.  Your own spacing may vary from any manual spec and/or other user depending on whether you have a filter and so forth in your imaging train.

 

Good point, Adam. I'm not sure if I have appropriate spacers to check it out before buying the part though. The tricky part is the OAG, but I don't really need that in the mix, so maybe I can work something out without it.

 

 

 

I've seen several figures for correct spacing of this flattener. Is anyone able to confirm, based on experience, what has actually worked?

 

I would suggest emailing Kevin at Skywatcher to get a clarification:  klegore@skywatcherusa.com

 

Kevin is very helpful.

 

 

Thanks mate.



#9 samuelpkco

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Posted 20 June 2016 - 04:26 AM

Hi leemr,

 

Happened to see this thread today and last night I was setting up the Esprit120 flattener with my ASI1600.

 

I was puzzled about the discrepancy in the manual too. 

 

Trying to find which one is correct, I used the DSLR focal plane marking

DSLR focal plane marking.JPG

to determine where the 75mm backfocus ends.

 

Since the Esprit is optimized for DSLR, using all its supplied adapters on the DSLR should guarantee the correct setup from which the 75mm distance can be measure from the focal plane marking on the DSLR body.

 

IMHO, I would stick to the 75mm backfocus provided by the manufacturer and not to do this by trial-and-error. The backfocus of any flattener/reducer is specifically designed to give the lowest aberration possible. Any deviation could mean the optics are working outside the design parameters. If a filter is added BETWEEN the CCD and the flattener, like in my case a 3mm thick filter, the light path is lengthened by 1/3 of that. So instead of 75mm, my setup has a backfocus distance of 76mm.

 

My finding is same as what the manual says, start of the male thread, the edge of the flattener.

(These are extracts of the Skywatcher Esprit 120 instruction manual, p8, p9)

photo 1.PNG

 

Page 9 is the only part that is not consistent with the rest so I think it is an error. 

photo 2.PNG

I added the red lines as a correction to my PDF manual.

 

I haven't got the chance to field test so I can't say this is 100% correct.

Any thoughts on this welcome!

 

This is my adapters between the CCD and the flattener:

image.jpg

The configuration is:

CCD-M42/0.75 female (ASI1600 nosepiece) > male-female M42/0.75 adjustable extension ring > male-female M42 fixed 5mm extension ring > M42 to M48 female (ASI1600 nosepiece) > M48 of the Esprit adaptor (....and there is the 48mm filter inside)

The total distance is 75mm+1mm adjusted via the adjustable T extension ring.

 

 

Hope this could help a bit.

 

Clear skies,

Samuel


Edited by samuelpkco, 20 June 2016 - 06:13 AM.

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#10 glend

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Posted 15 July 2016 - 03:39 AM

Lee, don't forget that the filter in a filter wheel behind the flattener will affect spacing. Using the general rule of 1/3, a 3mm filter will require adding 1mm to the spacing distance from the back of the flattener. I am going through this exact exercise setting up my 152mm refractor to work with the ASI1600/QHY filter wheel combo, and my Hotech Flattener. In my case my Baader 36mm filters are 2mm thick so i need to add 0.66mm of spacing from the flattener. There is a recent thread here that discusses spacing from flatteners and examines statements made by Don from Astrodon and other experts.


Edited by glend, 15 July 2016 - 03:40 AM.

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#11 leemr

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Posted 29 July 2016 - 09:26 PM

After having yet more issues with this, I was searching trying to find posts by the guy who had issues and I stumbled across my own thread. Thanks so much for that detailed post, Samuel, I really appreciate it. Your logic seems sound. I've now swapped out some spacers and have it within 0.5mm of the 75mm total, assuming my calipers are reliable :p

 

Samuel, did you ever get a chance to confirm that spacing? I too am trying to use this with the ASI 1600. I should be able to confirm it myself tonight anyway.

 

Glen, excellent point and thanks for raising that.




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