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Author Topic: TS Field Flattener CCD to Lens Distance  (Read 10752 times)

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Offline Nomis Elfactem

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TS Field Flattener CCD to Lens Distance
« on: 15:57:02, 08 June, 2010 »
Not sure if anyone will find this of us/interest but after getting myself a TS field flattener I struggled to find what the optimal distance the lens needs to be from the ccd for my Equinox 80 (f/6.2).  

I did eventually managed to find the required distance range for f/5.5, 6.6 and 7.5 so pulled together a chart to find the distance for my f/6.2.

Bob's your mothers live-in lover.....

S.

EDIT: Another piece of useful/less info that people may not know is that the "flange to focal plane" distance for a Canon EOS (all models I believe) = 44mm and 46.5mm for Nikon  :D

Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline Carole

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Re: TS Field Flattener CCD to Lens Distance
« Reply #1 on: 16:44:59, 08 June, 2010 »
That looks a useful chart Simon, if only I knew how to measure the lens to CCD.

Am copying off all this useful information for future reference.

Carole
Mount: NEQ6 (on pier), HEQ5 (for astrocamps),  Telescopes: SW ED120 Pro and SW Evostar ED80 pro, WO ZS71 APO, Cameras: Modified Canon EOS 450D, Atik 460EX, Atik314, DMK21, DBK, Dual rig options. Observatory: SkyPOD & PZT
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Offline markc

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Re: TS Field Flattener CCD to Lens Distance
« Reply #2 on: 17:44:00, 08 June, 2010 »
Simon

For what scopes and focal ratios is this flattener recommended?

I am still struggling to find anything that works effectively with a C80ED, SW ED80 or WO 110mm ED!!
CGEM mount,C11 Fastar,Hyperstar III, WO Megrez 110mm ED APO, Skywatcher 80ED,Celestron C80ED, Synguider, Canon 700D full spectrum modded, Astronomik CLS-CCD / UHC clip filters,Astronomik 2" 12nm Ha filter, Artemis 285 ccd, Atik EFW, Astronomik Type2c LRGB 1.25" filters,Astrotrac, Manfrotto 055XP tripod+496RC2 ball head,TW3100 Wedge,Canon EF 28-105mm f3.5-4.5 USM,Pentax Takumar SMC 200mm f/4

Offline Nomis Elfactem

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Re: TS Field Flattener CCD to Lens Distance
« Reply #3 on: 18:04:01, 08 June, 2010 »
Mark - my understanding is that it probably covers the widest range of f/ratios of any of them and is not bispoke to any particular scope (it says on Modern that it is for ALL refractors) which is why I went for it and probably why it's one of the most expensive.

Carole - I find a ruler quite useful  :laugh:

S.

EDIT:  Here the info from TS itself.  Mark - it states that it's good for f/5 to f/9 !

(http://www.teleskop-express.de/shop/product_info.php/language/en/info/p2646_Universelle-Bildfeldebnung-fuer-Refraktoren-von-f-5-bis-f-9---2-5.html)
Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline Nimbus

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Re: TS Field Flattener CCD to Lens Distance
« Reply #4 on: 18:58:54, 08 June, 2010 »
Hi All, I use one of these flatteners and found them very good.  

Carole, to answer your question:  The distance is measured from the join line between the TS flattener and the first spacer tube to the surface of your chip.  The handbook with your camera if you have one may give you the distance from the chip to the surface of the case. Simple maths and measurement should allow you to find the correct distance.  I should also add that Bern @MA has provided me with a couple of variable adjustment t-spacer tubes, which are perfect for setting the correct distance.  HTH Jim
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Offline Revs

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Re: TS Field Flattener CCD to Lens Distance
« Reply #5 on: 09:44:17, 13 July, 2011 »
Ah, now this is interesting. I'm currently trying to set the correct spacing for by MPCC to 1000D and was wondering if, on my f/4, the spacing should be on the high or low side of 55mm. My testing suggests <55mm but everything I read suggests >55mm, but there are no definitive answers. Any help here would be great! ;)
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Offline psjshep

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Re: TS Field Flattener CCD to Lens Distance
« Reply #6 on: 11:06:46, 13 July, 2011 »
I'm glad you resurrected this! I too struggled with my TS flattener... but I also have a problem with the camera not square to the focuser which compounds the issue...

Nice one!

Phil
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Offline chris.bailey

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Re: TS Field Flattener CCD to Lens Distance
« Reply #7 on: 19:58:51, 31 August, 2011 »
I do find it incredible that FF's are designed for very precise spacing to chip over a narrow range of FL and yet the manufacturers struggle to provide such key information. I have had the devils own job getting W/O to give the spacing for their TMB FF for FLT as all their charts used to show the distance from the crown point of the FF lens that is pretty hard to measure from. After numerous emails they then showed a measurement from the back of the T adaptor.I have 3 of them and they are all different so a totally useless pice of information. When finally they come up with the distance from the back of the T mount plate their suggestion is an optimum of 54.98mm for the FLT110. 54.98mm mind not 55mm. That is now on their latest offering on the W/O website. 54.98mm is pretty definitive. Try measuring that with a ruler let alone finding a T spacer to 0.2mm of accuracy.
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Offline Carole

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Re: TS Field Flattener CCD to Lens Distance
« Reply #8 on: 08:07:51, 01 September, 2011 »
I did indeed copy and keep this chart but had forgotten who had posted it. Recently bought a new flattener and used this chart and got the spacing spot on.

Thanks Si

Carole
Mount: NEQ6 (on pier), HEQ5 (for astrocamps),  Telescopes: SW ED120 Pro and SW Evostar ED80 pro, WO ZS71 APO, Cameras: Modified Canon EOS 450D, Atik 460EX, Atik314, DMK21, DBK, Dual rig options. Observatory: SkyPOD & PZT
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Offline Nomis Elfactem

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Re: TS Field Flattener CCD to Lens Distance
« Reply #9 on: 10:28:34, 01 September, 2011 »
Your welcome Carole  :thumbup:

I've also re-attached the chart as it appears it got deleted as part of the space saving clean-up we did, so it's back now.

Chris - I think the problem is that there are so many different combinations of equipment that it would be very difficult for a manufacturer to state a distance as it all depends upon the focal ratio of the scope.  That was the reason I took the three figures quoted for the TS flattener and created the chart, as it didn't cover the f/ratio of my Equinox.

Having said that I'm not sure why the manufacturers can't just create a chart like I've done.  It's heardly rocket science (creating the chart that it).

I've also noticed that I only did it down to f/5.... if anyone needs it lower than just let me know and I'll amend.

S.
Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline chris.bailey

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Re: TS Field Flattener CCD to Lens Distance
« Reply #10 on: 10:49:16, 01 September, 2011 »
Simon. I wholeheartedly agree in terms of a general purpose FF but my W/O example is very scope specific. W/O simply failed to understand that giving a spacing measured from the crown of a lens that is all but inaccessible is not very helpful! Took a year of emails for them to finally grasp what I was trying to get at. My, albeit limited, experience in the use of FF's is that the lens to chip distance is very critical for some FF's. With my W/O TMB FF a couple of mm makes a huge difference when measured with CCD Inspector. I bought the thing to get a flat field, not a curvy one! As you say, FF manufacturers are clever people and should be able to provide guidance along the lines of the chart you have produced. These are not cheap items and giving users the data they need to use them is not asking too much.
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Offline Nomis Elfactem

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Re: TS Field Flattener CCD to Lens Distance
« Reply #11 on: 11:29:55, 01 September, 2011 »
Arrrh, point taken about general FF's - totally agree on everything else :thumbup:
Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline chris.bailey

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Re: TS Field Flattener CCD to Lens Distance
« Reply #12 on: 12:14:08, 01 September, 2011 »
Simon, As you might be able to tell, my tale of W/O woe was one of the more frustrating experiences of my life :-) To my mind it was like buying a car and not being told if it ran on petrol or diesel!
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline Nomis Elfactem

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Re: TS Field Flattener CCD to Lens Distance
« Reply #13 on: 12:51:27, 01 September, 2011 »
 :rofl:

Sorry, Chris... I shouldn't laugh but your analagy was quite funny !

I totally agree though... it really isn't difficult to provide as a matter of course the required info that is applicable to the real world not the confines of a lab or workshop.  I guess that's one of the downsides of a "manufacturer" also being at the customer facing end.  I've been doing quite a bit of work recently with a major international consumer goods manufacturer and their marketing is so product focused they've completely forgotten who the customer is.

S.  :thumbup:
Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline astrograph

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Re: TS Field Flattener CCD to Lens Distance
« Reply #14 on: 16:28:52, 09 March, 2013 »
This chart is not actually of great use. I wish it were because it would make life a lot easier. The benchmark back focus distances for the TS 2.5" is as follows. These used to be quoted by TS.

F8 / F7             91.5mm
F6.5                 99mm
F6                   106mm
F5.5                111mm

If you work it out you will see this is not a nice straight line on a graph. I must stress that on an actual scope things may change because of the individual field curvature of different scopes. I know that 99mm for an APM 107 F6.5 is correct because I have tested it on a Nikon APS sensor which has a 28mm image circle and there was no discernible difference in focus or exposure at the edge of frame. One day I will get round to trying it on a full 44mm.

TS actually recommend doing FHWM to establish the correct distance. Christoph at TS actually recommended a starting point of 119-121mm for an F6.5!

 

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