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  #1  
Old 29-05-2011, 10:24 PM
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Visionoz (Bill)
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Any Good Field Flattener for Equinox 80mm OTA?

Hi

Would like to know if anyone here has used any particular brand of field flattener for an 80mm OTA and can recommend it?

I've tried the HoTech one (purchased from MyAstroshop) on an 120mm ED OTA and it works a treat, however it just does'nt do the job on the Equinox 80mm ED OTA

With & without the FF, the 80mm has elongated stars in all the four corners of the image and I reckon that I lose about 33% of the image because I'd have to crop it off - though I wonder if by using a 2.5" focuser (MoonLite custom LF version) instead of the 2" one that I've actually created the problem for myself - on the other hand could the spacing to the CCD chip be a factor? ie it is different for a 120mm than for an 80mm refractor?

The FF is currently just between the CCD camera and the focuser like this:
CCD -> FF -> Ext tube -> into the MoonLite focuser

Any help in pointing me in the right direction would be greatly appreciated

TIA
Cheers
Bill
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  #2  
Old 30-05-2011, 08:23 AM
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troypiggo (Troy)
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Not sure about the effects of your focuser, but I've had the best results with the William Optics Field Flattener 4 on my ED80. My focuser is the GSO 10:1 crayford. I imagine the only dramas would be more-so on the length of the focuser rather than the diameter, because the WO FF4 does put a bit of distance between the camera sensor and the scope OTA.
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  #3  
Old 30-05-2011, 11:04 AM
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Thanks Troy

The distance/length should not be an issue as I have to still crank out the drawtube (4.5" type) out a fair bit now - shame that Perth hasn't any astro-shop of any worth whereby one could at least give it a trial before spending the spoondoolas and then find out that it is not suitable!!

I'm sure that there are many others on IIS who are using all manners of this type of accessories Troy; not just you and me, so I'll have to wait and see before I rush out to try get something to fix my issue!

Cheers
Bill
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  #4  
Old 30-05-2011, 11:16 AM
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Hi Bill,

I don't think I will be of much assistance yet, but I myself have just received the P-Flat 4 from William Optics. With the strength of the dollar together with free delivery, it was too good an opportunity. I was trying to find a flattener for both my Skywatcher ED120 and ED80. I originally was interested in the Skywatcher/Orion flatteners however I would have required 2 as they are not transferable. The other significant issue with them is that they are M48 thread which does not allow a CCD to be connected without some kind of adapter which would need to be custom made.

Anyhow..... just waiting for a clear night so that I can do a test image. I have it all sitting ready to go. I fitted the P-Flat 4 to the QHY8L and it is a nice solid threaded connection ( together with the Moonlite focuser on the ED120.... seems very solid).

Could be clear in Adelaide tonight so fingers crossed!

Cheers,

Daniel
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Old 30-05-2011, 08:08 PM
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Thanks Daniel

That's good timing - yep I did think about those from SW/Orion and then heard from here that others required a "special" adapter-to-T-Ring so turned me off - I already had the HoTech previously for my 120 BD - just need to start using the Equinox80 and hence the test and search now after the results of the test showed it was "useless" for the 80mm

Never mind Daniel, we're both in the same boat so to speak - at our level we'll just try to help ourselves and you have a similar CCD size to mine anyway (mine's a Orion SSDSI Pro; same chip I believe!) so I'd be interested to see how your results pan out with the 80mm OTA - if it proves useable for both the 120mm & 80mm then I'd go and purchase one too! That's the model that's adjustable isn't it?

TIA
Cheers
Bill

Quote:
Originally Posted by DJ N View Post
Hi Bill,

I don't think I will be of much assistance yet, but I myself have just received the P-Flat 4 from William Optics. With the strength of the dollar together with free delivery, it was too good an opportunity. I was trying to find a flattener for both my Skywatcher ED120 and ED80. I originally was interested in the Skywatcher/Orion flatteners however I would have required 2 as they are not transferable. The other significant issue with them is that they are M48 thread which does not allow a CCD to be connected without some kind of adapter which would need to be custom made.

Anyhow..... just waiting for a clear night so that I can do a test image. I have it all sitting ready to go. I fitted the P-Flat 4 to the QHY8L and it is a nice solid threaded connection ( together with the Moonlite focuser on the ED120.... seems very solid).

Could be clear in Adelaide tonight so fingers crossed!

Cheers,

Daniel
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  #6  
Old 31-05-2011, 08:31 AM
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Hi Bill,

Well I was lucky enough to have some clear skies last night, so I did some testing with the flattener attached to both the ED120 then the ED80. The good news is that the QHY8L came to focus on both scopes, however, I could not get "round" stars in the corners. On the flattener there is a scale indicating distance from lens to chip (66..76..86). I basically tested at 5 different settings on both scopes, roughly equating to 66, 71, 76, 81 and 86 mm. Maybe the sweet spot needs to be a lot more accurate so I will need to do some more testing. The other thing that comes to mind, I want to check the actual distance I am getting from the imaging chip. I have threaded the QHY8L directly to the flattener, which seems to me to be the design intent. Maybe, with the inherent design of the QHY8L it is too close a distance, so maybe I will require a "male-female T thread extender". Not too sure if these exist?

Anyhow, hopefully we can get some more comments. I might try and send Troy a PM, as he seems to be having good success with this flattener, his ED80 and 40D.

Cheers,

Daniel
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  #7  
Old 31-05-2011, 08:45 AM
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I have just been looking at the specs on the flattener and the QHY8L. Now most of the WO scopes require around the mid 70's in terms of distance to the chip. The QHY8L sensor is 20mm to the front location surface. On the flattener it is 24.1 mm. To achieve a mid range 76mm, I am roughly 32mm short. I reckon I need to find a t-thread extension of about 30mm.

I hope this makes sense.

Cheers,

Daniel
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  #8  
Old 31-05-2011, 09:41 AM
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As I understand it, the scale on the FF4 is set the distance from camera sensor to rear element in the FF4. For a DSLR it's 66mm which includes about 10mm for the EOS adapter ring. Not sure about the QHY8.
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  #9  
Old 31-05-2011, 09:49 AM
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Thanks for that Troy. I am pretty sure a 30mm extension will be needed for the QHY8L. It is only 20mm from the sensor to the mounting face on the camera. Worth a try!!

Cheers,

Daniel
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  #10  
Old 31-05-2011, 07:42 PM
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If you have a Baader 2" nosepiece you will fInd this is about 30mm. It makes a good T thread extension.
Gary
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  #11  
Old 31-05-2011, 08:01 PM
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Thanks Daniel & also Troy & Gary

OK so there is a difference in the last-element-to-sensor distance for different focal length OTAs - I wonder where could we find these details from?

That would then perhaps be what I need too - an extension tube of "X"
length to give the correct spacing - certainly it is best to have the FF to attach to the CCD and if requiring an extension would solve the issue then that's great! Experimenting with my present lot of accessories is necessary; it's only for the 80mm that I need a solution for with the HoTech FF since I'm able to get round stars to the corners - see here for an example

Will need to wait for the rain to clear before being able to do any testing now

Will post results after

Cheers
Bill
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  #12  
Old 04-06-2011, 11:57 PM
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Quote:
Originally Posted by DJ N View Post
Hi Bill,

... so maybe I will require a "male-female T thread extender". Not too sure if these exist? ...

Cheers,

Daniel
Hi Daniel

I've been researching a bit since the last post - no I haven't found an outright solution yet - but I've discovered some documentation from the HoTech website in particular reference to my HoTech FF and indeed it seems that the spacing from the end element of the FF has to be overall a maximum of 55mm to the sensor chip!!

And yes there is a supplier of those "T2-male-to-female" extenders; see here: http://myastroshop.com.au/products/cam-adapt.asp - I'll be ordering the 40mm one for myself as it seems that I've not been using the FF in the correct fashion as regards to the spacing - apparently this 55mm spacing is the same spacing for the EOS camera as I've noted this figure being always mentioned in many articles on the internet

Have to wait till next week since it's a long weekend here

HTH
Cheers
Bill
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  #13  
Old 05-06-2011, 05:25 PM
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Quote:
Originally Posted by Visionoz View Post
Hi Daniel

I've been researching a bit since the last post - no I haven't found an outright solution yet - but I've discovered some documentation from the HoTech website in particular reference to my HoTech FF and indeed it seems that the spacing from the end element of the FF has to be overall a maximum of 55mm to the sensor chip!!

And yes there is a supplier of those "T2-male-to-female" extenders; see here: http://myastroshop.com.au/products/cam-adapt.asp - I'll be ordering the 40mm one for myself as it seems that I've not been using the FF in the correct fashion as regards to the spacing - apparently this 55mm spacing is the same spacing for the EOS camera as I've noted this figure being always mentioned in many articles on the internet

Have to wait till next week since it's a long weekend here

HTH
Cheers
Bill

Hi Bill,

Thanks for that......... I ordered the spacers (the pack with the 3,6, 10 and 20mm spacers) from Myastroshop on Wednesday, so with any luck should have them in the next day or so. Cannot wait to give it a go. I reckon I need around 32mm...give or take.....

Cheers,

Daniel
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  #14  
Old 14-06-2011, 11:05 AM
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An update : well I received the spacers and had a bit of a testing session. In summary, there was good news and bad news.......

I estimated that I required around 30mm extra spacing between the Pflat-4 and the QHY8L. However, on both the ED80 and the ED120, I could not achieve focus. I double and triple chaecked, and basically I had to have less backfocus!! I played around with different configurations and I finally received some decent results with the ED80 and a 6mm T thread spacer between the flattener and CCD with the flattener set at "86" (I will need to post the test image....). I could achieve focus with the ED120 and the 6mm spacer and the flattener set at "66", however I was getting very egg shaped stars in the corner... far worse than I get without a flattener.

So in summary, I am getting some decent results with the ED80 however cannot achieve the same with the ED120. This is starting to hurt my head. Maybe I am doing something wrong..... I don't really want to cut the tube on the ED120 (just kidding ).

Just need some more clear nights to keep testing.......

Cheers,

Daniel
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  #15  
Old 14-06-2011, 12:00 PM
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mswhin63 (Malcolm)
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I received my Field Flattener from TS yesterday, as a package it came with a 40mm spacer to suit the scope. I have yet to try it out due to the rain. Give you feedback.

It came as a package though but the single price is quite high otherwise.
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  #16  
Old 14-06-2011, 11:03 PM
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Hi Daniel

I've also got my spacers in last weekend but the inclement weather has stuffed my plans

I think I've researched enough and got up to speed with the "backfocus" nonsense (not really, as it affects how much we have to make up with spacers/ext tubes etc!!) and for my Orion SSDSI Pro v1 CCD apparently the flange distance to the sensor chip is supposed to be 14.5mm - now it being that the HoTech FF is supposed to be set 55mm from the sensor chip it means I've got to bridge that 55mm less the 14.5mm with the spacers!

BTW what is your QHY8L's flange distance to the sensor?

So until I can see stars and do a PA I can't experiment anymore till then

But what is strange though is that the HoTech works OK with the 120mm OTA without my being concerned (ignorant is the correct word here!) of the spacing requirement - I actually just screwed the T2 threaded end fitting straight into the camera opening (got the idea from h0ughy here who did just that with the HoTech and his 127mm NG OTA) - and it did the job pretty good - however would not work for the 80mm OTA - perhaps the native FOV of the scope plays a part in the equation; my premise is that the 120mm has a narrower FOV vis-a-vis the 80mm OTA which is of course much wider ... anyway just a thought!

HTH
Cheers
Bill
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Old 14-06-2011, 11:18 PM
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Yeah that damn weather!
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  #18  
Old 15-06-2011, 01:18 AM
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Quote:
Originally Posted by Visionoz View Post
Hi Daniel

I've also got my spacers in last weekend but the inclement weather has stuffed my plans

I think I've researched enough and got up to speed with the "backfocus" nonsense (not really, as it affects how much we have to make up with spacers/ext tubes etc!!) and for my Orion SSDSI Pro v1 CCD apparently the flange distance to the sensor chip is supposed to be 14.5mm - now it being that the HoTech FF is supposed to be set 55mm from the sensor chip it means I've got to bridge that 55mm less the 14.5mm with the spacers!

BTW what is your QHY8L's flange distance to the sensor?

So until I can see stars and do a PA I can't experiment anymore till then

But what is strange though is that the HoTech works OK with the 120mm OTA without my being concerned (ignorant is the correct word here!) of the spacing requirement - I actually just screwed the T2 threaded end fitting straight into the camera opening (got the idea from h0ughy here who did just that with the HoTech and his 127mm NG OTA) - and it did the job pretty good - however would not work for the 80mm OTA - perhaps the native FOV of the scope plays a part in the equation; my premise is that the 120mm has a narrower FOV vis-a-vis the 80mm OTA which is of course much wider ... anyway just a thought!

HTH
Cheers
Bill
Thanks for that Bill. Maybe require 2 different flatteners for each scope after all . I was hoping that the WO would work on both.

From the manufacturers specification, for the QHY8L, the distance from the CCD to the front location surface is 20mm (or 23mm with the tile adjusting ring).

Anyhow, here is a test image with the ED80 (300sec with a 90% illuminated moon)....... please excuse the processing....... no flats either........was taken just to see the flattener effect.

Cheers,

Daniel
Attached Thumbnails
Click for full-size image (Eta Carina 10Jun11 ED80 QHY8L PFlat4 IIS.jpg)
198.3 KB71 views
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  #19  
Old 15-06-2011, 09:08 AM
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Hi again Bill,

You mentioned that you have had success with the Hotech flattener and the ED120. Do you have any images that I could have a look at. I am honestly thinking of purchasing this same flattener for use with my ED120. I like the fact that it is only a flattener and not reducer. Whereas for the ED80 and the P-Flat4 combination, I like that it reduces about 0.75x.

cheers,

Daniel
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Old 15-06-2011, 10:08 AM
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Quote:
Originally Posted by DJ N View Post
Hi again Bill,

You mentioned that you have had success with the Hotech flattener and the ED120. Do you have any images that I could have a look at. I am honestly thinking of purchasing this same flattener for use with my ED120. I like the fact that it is only a flattener and not reducer. Whereas for the ED80 and the P-Flat4 combination, I like that it reduces about 0.75x.

cheers,

Daniel
Hi Daniel

Yep the FR for your 80mm seems to be working!

I referenced a link in my post#11 earlier on - but here it is again: LINK

This was with the 120mm OTA + HoTech FF mounted directly to the CCD using the T2 male thread of the FF rear end with no "correct spacing" in mind!

It is looking that way Daniel that two different FFs are needed; one for each - but wait on a bit if you can before purchasing the HoTech - I've got to test out the 2.5" FF from TS (Teleskop-Service.de) yet but have to wait for clear weather - if it works it will mean that I'll be using the TSflat25 (click here) only - I was provided with all the correct spacers etc to suit both the 80mm & 120mm OTAs - so will post back here the results

Reason I went for the 2.5" one (they have a 2" as well) is that both my OTAs are fitted with custom sized 2.5" MoonLite focusers (the standard size is 2" for those OTAs but I ordered the 2.5" LF with custom flanges; did cost a fair bit but one of them has the stepper motor drive; just beaut!)

HTH
Cheers
Bill
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