Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Esprit 80 Unboxing

JohnC64

Recommended Posts

JohnC64

JohnC64

Posted
  • Author
Posted

Original email i sent and the reply from SkyWatcher.

John,

Yes, the Esprit 80ED requires 75mm back focus for a flat field. Which DSLR are you using? 

Customer Support
-----------------------
Sky-Watcher USA
475 Alaska Avenue, Torrance, CA 90503
310-803-5953



-----Original Message-----
From: [xxxxxxxxxxxxxxxxxxxxxxxxxxx]
Sent: Thursday, October 31, 2013 1:49 AM
To: support@skywatcherusa.com
Subject: Esprit 80ED Supplied flattener back focus

Hi there,

I wonder if you can help me with an issue that i have with imaging with an Esprit80 ED using the Flattener and a Canon DLSR.

I am having a problem with distorted stars on the left of my image.  I have connected the flattener to the scope and connected the DLSR adapter to it.  I note that the DLSR adapter when connected to the camera gives 55mm distance from the cmos chip to the front of the adapter.

If i read this article on cloudy nights, it mentions (Skywatcher USA)  that the back focus off the flattener is 75mm.

Is the reason why I am getting odd shaped stars because my camera is only 55mm from the flattener and not 75mm?.  If I purchase a 20mm M48 extension tube and insert after the flattener, will this correct the issue?

Many thanks for any information

Link to comment
Share on other sites
  • Replies 110
  • Created
  • Last Reply
FLO

FLO

Posted
Posted

measured it with vernier's and got 11.08 - so looking at 11.1mm  so definitely a sed-80

JOhn

Ah well, there goes my theory :smiley:

I have Skywatcher's schematic for the flattener in front of me, the spacing is definitely 54.9mm from the mating surface. 

It might be worth checking your focuser is square to the optical axis (easily done with a laser and a sheet of paper) but you shouldn't have to. 

I think you need to contact your supplier. 

Link to comment
Share on other sites
FLO

FLO

Posted
Posted

Groan :(

Unfortunately 55mm(isn) spacing is the norm Gina.

I would like to see longer spacing too but there are a lot more DSLR cameras out there than dedicated imaging cameras so manufacturers cater primarily for them. 

Link to comment
Share on other sites
Gina

Gina

Posted
Posted

One thing I could do - focus the scope with that house (a mile away that I use for setting up) in the middle then move the mount to put it in each corner and check focus.  In fact I could do that with a DSLR - I have an 1100D amongst others :D  Have to see what adapters I have.  I could try it straight on the scope tomorrow as long as the horizontal rain isn't coming from the east :D  I have EOS to T2 adapters and various T2 extension tubes so should be able to try trhe 75mm from FF surface.  Not as good as stars but who knows when I shall see any of them again...

Link to comment
Share on other sites
Gina

Gina

Posted
Posted

Unfortunately 55mm(isn) spacing is the norm Gina.

I would like to see longer spacing too but there are a lot more DSLR cameras out there than dedicated imaging cameras so manufacturers cater primarily for them. 

And I thought Skywatcher were moving upmarket!

Actually, I'm in the process of making a mono DSLR (450D) with filter wheel built in such that the back focus will be retained.  Mainly for use with lenses for widefield but I expect to try it with the Esprit 80ED as well.

Link to comment
Share on other sites
Gina

Gina

Posted
Posted

Hope you're right John :)  We need to get this business connfirmed one way or the other.

As for my setup - in the final version I plan to put the Esprit on top of the MN190 and have the OAG and guide camera on that.  Meanwhile I can do without guiding and see how well the EQ8 works unguided.  If the new spacing figure is right I'll have to sort out extension tubes again :D  Another day will do for that :)  "My bwain hurts Bwian" :D

Link to comment
Share on other sites
JohnC64

JohnC64

Posted
  • Author
Posted

and a fit uploaded with IDAS LP filter in line 

https://www.dropbox.com/s/uyh3ksi14ovwb1j/m45testshotfilter.fit

looks like this was causing my problem and inadvertently added to  the confusion.  So question - how do i use filters (LP, HA)  for  DLSR with this scope - I think that the answer is that i don't. and may have to switch to ccd

John

Link to comment
Share on other sites
Sp@ce_d

Sp@ce_d

Posted
Posted

and a fit uploaded with IDAS LP filter in line 

https://www.dropbox.com/s/uyh3ksi14ovwb1j/m45testshotfilter.fit

looks like this was causing my problem and inadvertently added to  the confusion.  So question - how do i use filters (LP, HA)  for  DLSR with this scope - I think that the answer is that i don't. and may have to switch to ccd

John

Ok.. you'll need to put in in front of the reducer. On the 80ED I put it in the nose of a FLO adapter.. Will that one work with the Esprit flattener Steve?

EDIT: forgot link.. http://www.firstlightoptics.com/adaptors/flo-adapter-for-skywatcher-focal-reducers.html

Link to comment
Share on other sites
Gina

Gina

Posted
Posted

Got your FITS file John, after over an hour downloading but it won't open with FITS Liberator :(  But if you say it's fine that's good enough for me :)  Looks like the spacing query is answered :)

Back to the drawing board then with my spacing.  Initial quick calculation (in my head) would see to indicate that I'd need a 5mm extension tube - which I haven't got, of course.

Link to comment
Share on other sites
Gina

Gina

Posted
Posted

I've got it open in Preview on my MacBook and have zoomed in until I can see the pixels and I can't see anything wrong at all.  All the stars are nice and round wherever I look in the image.  I can see the processing in the form of dark halos which generally come from sharpening.  And there's the usual colour noise you get with DSLRs but I can see nothing wrong with the scope - the image is definitely FLAT.  :)

Link to comment
Share on other sites
Gina

Gina

Posted
Posted

:grin: ...

Zoom in & compare the stars at the bottom to the top.. top ones towards the left corner are going eggy. 

Not on my screen they're not.  Can't get the screen grabber to work so can't show you :(

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.