Esprit 80 Unboxing

[ollypenrice]

Well, focus could reduce the visible effects of curvature by getting a better compromise across the chip but slight mis-focus won't create curvature that isn't there, so this is not a very flat field as is.

Psychobillly's advice to focus on a star located at the intersection of the 1/3 lines may be useful to you in seeing how far you can mitigate the distortion. Also some experimantation with chip distance may be needed since the manufacturers are not always as sharp on this as we might like them to be.

To be honest I'd be a little concerned by this test. Does the flattener have any tilt facility? This is present on the Takahashi reducer in the form of three radial screws.

Olly

[Sp@ce_d]

John did you see this thread about the spacing over on CN?

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5950387/page/1/view/collapsed/sb/5/o/all/fpart/1

I'm thinking the supplied camera adapter is the same as the standard SW one that makes the 55mm required with their 80ED reducer.

[JohnC64]

Hi Sp@ced,

Yes the camera adapter supplied is one that gives 55mm of chip distance.  I had fitted that directly to the back of the reducer and racked out the focuser to give me focus.  As the back focus on the Esprit is quoted as 75mm, is that from the back of the reducer  - so i might need a 20mm length spacer to reach the correct distance?

Ah more research required i think

Many thanks for the info

John

[swag72]

Hi Sp@ced,

Yes the camera adapter supplied is one that gives 55mm of chip distance.  I had fitted that directly to the back of the reducer and racked out the focuser to give me focus.  As the back focus on the Esprit is quoted as 75mm, is that from the back of the reducer  - so i might need a 20mm length spacer to reach the correct distance?

Ah more research required i think

Many thanks for the info

John

Isn't the 55mm of chip distance from the reducer to the camera sensor - So it is 55mm regardless of how much you rack out the focuser. As long as you have the 55mm, then that should give you your flat field, you don't need to take into account any back focus within the scope itself, as long as it reached focus, that's OK.

That's how I understand it anyway. Have you got the 55mm distance at the moment?

[ollypenrice]

Sara's right. The quoted spacing for a flattener has nothng to do with the amount of draw tube length that's needed to focus. It's the back of the flattener to chip that matters. Add about a third of the thickness of any glass in the system (filters, chip window) to the quoted distance to allow for refraction. It can be very critical.

Olly

[JohnC64]

Just researching what the distance should be from the back of the flattener. 75mm or 55 mm.  The cloudy nights article appears to suggest 75mm,(with answers from Skywatcher USA)  but the adapter supplied with the scope gives 55mm.

John

[swag72]

FLO should be able to confirm I would expect. If it's 75mm, then you need to put an extra 20mm in between the reducer and the chip. What camera are you using with it? A CCD or a DSLR?

[JohnC64]

Hi Sara,  

using a Canon EOS 1100D, quick image here http://stargazerslounge.com/topic/198225-esprit-80-unboxing/?p=2087532  and here  
 

[swag72]

If you're using a DSLR then the 55mm spacing should be spot on with the reducer (if it is indeed 55mm). Those SW reducers have the spacing distance optimised for DSLR's.

I'm not sure how a manufacturer can quote a figure of 55mm and then get it so wrong if it is 75mm. 20mm in spacing is utterly critical I would suggest, hell even 2mm makes a difference.

Just a thought, the 75mm that is being mentioed on CN is for this reducer? Not for people that are trying out a TRF2008 for example?

[JohnC64]

post 1 in the cloudy nights thread appears to suggest this flattener.  " with the included field flattener"  and Skywatcher USA then suggest the distance is 75mm in posts 7 & 9

its odd though that you get a DLSR  adapter with the scope that just gives 55mm.  Its a fail waiting to happen if its actually 75mm.

Time will tell.  Just pinged an email to Skywatcher to get the information from the horses mouth.

John

[swag72]

I've had a close look at your M45 .fits file that you put in the dropbox, I don't know how closely you've looked at these - I hope that correct spacing with the flattener can sort the stars out. They seem to be flaring out to the left and not tight in this image. I was a little surprised to see this in the middle of the frame though.

[ollypenrice]

I was concerned that the distortions were too much for a small chip distance error but if the error is 20mm then that's enormous and puts any judgement on 'hold' until the distance is to spec. Why the blessed chip distances are not printed loud and clear on all flatteners is entirely beyond me. It would be a blessing for the consumer and a blessing for the manufacturer because it would improve the quality of images taken with their scopes and reduce the number of false alarms.

One difference between premium makers and budget challengers, so far, is that accurate optical infomation is available from the old guard. Chip distances, spot sizes, imaging circles. We do need this information.  I just bought the TEC flattener (expensive!) but the flat field is large (and specified) and the chip distance is clearly stated and was absolutely perfect so that I could order a custom spacer with confidence. I added a mm for a filter and it was bang on across a full frame chip. That's how it should be and since you can't build a scope without knowing this information it should be out there on the net.

Olly

[FLO]

One difference between premium makers and budget challengers, so far, is that accurate optical infomation is available from the old guard. Chip distances, spot sizes, imaging circles. We do need this information. 

When used with their flatteners the Esprit 80 has a 33mm field coverage and the Esprit 100 40mm (the Esprit 120 & 150 cover 44mm). This was mentioned back in September when we announced the two models were incoming. I am sure we have spacings too. I'll gather the details together later today then add them to our website's product descriptions pages. Things can be a little messy during a product launch  

HTH, 

Steve 

[Gina]

I was very surprised that the telescope user manual didn't even mention the field flattener   I'm afraid Skywatcher have just gone down a notch in my estimation.  Why-oh-why do so many manufacturers produce decent/great kit then let themselves down with poor documentation? 

"Disillusioned of Devon"

[JohnC64]

The "Manual"  that i received was just the generic "Astronomical Telescope user guide"  from OVL which was just included in the outer box.  I haven't found one on the skywatcher site either.  Guess thats the price you pay when you are an early adopter

John 

[Sp@ce_d]

The way I've understood this one, having followed Fogboundturtles experience during the summer, is its 75mm spacing sensor to flattener. I'm hoping it is because that gives a much more sensible spacing for accessories than the often tight 55mm.

[JohnC64]

Cheers Sp@ced thats how I read the thread too.  I'll wait to hear what Skywatcher says and get a 48mm diameter spacer. 
John

[Gina]

The "Manual"  that i received was just the generic "Astronomical Telescope user guide"  from OVL which was just included in the outer box.  I haven't found one on the skywatcher site either.  Guess thats the price you pay when you are an early adopter

John 

Well it shouldn't be!  To use a telescope with a field flattener you NEED to know the back focus.  Where all the adapters fit can be just trial and error and common sense.  But the camera sensor HAS to be placed at the RIGHT DISTANCE from the FF for the FF to work correctly - it is it's SOLE PURPOSE.  It's a FIELD FLATTENER that only works with the right back focus. 

Sorry for the rant but I feel severly let down by Skywatcher.  It really isn't good enough!

[JohnC64]

Ok can I pick the collective brains on here?

So it looks like I have to fill 20mm but as I want to use a filter too, either a 2" IDAS LP Filter or a Ha Filter I will need to add another 1mm,  So bringing it up to needing 21mm spacing.  Is this right?  (I'm never sure if I need to add or subtract the part of the thickness of the filter.)

When I used the scope the other night, I had the filter screwed inline into the EOS adapter and whilst it works, it is inconvenient if I want to do Ha and RGB in the same night as I would have to refocus etc

I then got to thinking that I may as well make use of that gap and started to look at a Filter drawer.  The Gerd Neumann is tantalisingly close at 22mm optical path length but from reading around, I need to be sub millimetre accurate on the spacing.

Now Telescop Express do a filter drawer with 15mm optical path so I would need to add a 6mm spacer in there too. So two 3mm spacers would do it (couldn't find a 6mm one)

Can someone sanity check  my assumptions above and offer any advice on if I could "Get away with" the Gerd Neuman all in one unit

Many thanks John
 

Links to the filter drawers here

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3979_Filterschublade-inkl--1-Einschub-fuer-2--Filter---15mm---M48-Ansc.html
http://www.gerdneumann.net/english/filterzubehoer-filter-accessories/filter-drawer-system-filter-schubladen-system.html

And the spacers

http://www.teleskop-express.de/shop/product_info.php/info/p6435_TS-3mm-Extension-Ring---2--Filter-thread-M48x0-75mm---male---female.html

[jezhughes]

As much as it sucks, to be fair to Skywatcher i rarely see FF spacing info supplied with other reducers/flatteners, even more costly ones than the FF that comes with this scope.

Doesn't seem to be the done thing, for whatever reason..

[steppenwolf]

I think the lack of spacing information and the original reliance on the assumption that we all use DSLR cameras is a real issue but in fairness to Sky-Watcher, they are no worse than many other reputable suppliers in this regard. I have recently taken delivery of a rather expensive Takahashi reducer - now this did come with an instruction sheet - entirely in Japanese and with a set of pretty meaningless diagrams referring to an adaptor known as a CA-35 of which there are at least three different variants!!

This is not a problem peculiar to Sky-Watcher or new product releases in general, this is an industry-wide problem and one that it looks like FLO might be trying to resolve locally although it is the manufacturers who should be making this information readily available in the first place. I get more private technical queries about spacing issues than anything else and this is on a wide range of equipment manufacturers!

I really hope that John's spacing is out by 20mm because if it is, it shines a totally new light on his Esprit and we can start anew with reviewing it with it correctly set up for imaging!

[Gina]

I believe I have mine set up correctly and it's ready to go out onto the mount.  It seems from the weather forecast that we might just get a slight chance on Monday but who knows!  Meanwhile, I'll use the next day or two to attach a focus motor.

[JohnC64]

Sounds great Gina.

I have had a reply from Skywatcher, who confirmed that the correct distance from the back of the flattener is 75mm.  But they also said that I should have everything needed to connect a Canon DLSR to the scope!!
I sent them the measurements that add up to 55mm with the supplied adapters.  I know a lot of people will be using CCDs with this scope but surely i can't be the only person to have attempted to connect a DLSR.

I have my spacers on order and hopefully they will come soon.  sunday Night/Monday looks about right for me too to have another go.

To be adjourned until after the weekend

The email from SW

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

 

[Coco]

Sounds like your closing in on getting it tweaked John and for that I am happy for you.

For the sake of a few cents why didn't sky watcher put a sticker on the OTA with this information.. or a piece of paper in the box?  Maybe FLO might do this for their customers, I hope so..

I can see someone's initial excitement spoiled unless they read these posts...

[Gina]

So a DSLR needs 20mm extra - that's interesting, as I think that's the thickness of Atik's EFW2  

EDIT - Ooops just checked. - no, it's 22mm - oh well