Elephant Nebula through Canon lens

[physicus]

This has had only 3 hours or so integration in Ha, so noise levels will drop with more exposure.  But it was more a test of how my Canon 100-400L telephoto would perform adapted for use with the Atik460 camera. 

For some time I've been wanting to go wider than my C9.25 allows, and it's  inevitable I'll at some point complement the SCT with a refractor; but I wanted to see what my (not inexpensive!) camera glass could do first.  On the strength of this pic I'm less inclined now to rush at  the likes of the Optic Star, using my camera lenses for really wide field and leaving more pennies for a larger refractor more suited also for visual work. 

Star shape and flatness are not too bad, and looking at individual subs, a slight ovality is likely  due to flex in the mounting or intermittent mirror shift in the guiding SCT - not guiding or the lens itself.   The adapter is home made from an old lens cap and 1.25/T2 nose piece, with the filter screwed into the noisepiece which projects into the rear of the lens.   Also on the strength of this experiment, I've ordered the TS EOS to T2 adapter as a more secure solution, probably with lower flex too.   The lens was set to 250mm f6.3.  It's a pain setting aperture, involving setting it on the 7D body then unfastening the lens with the DOF preview pressed and the camera switched on.   In theory it's a pain changing filters too, but in reality with narrowband, it's hours between changes anyway.  The eight spoked spikes are caused by the camera diaphragm.

[StevenWhatley]

Lovely image !!

[John Baker]

Great work

Sent from my iPhone using Tapatalk

[Stardust]

Very nice, I've been trying widefield with lenses too. I was advised to leave wide open and cut a circle of plastic to stop down so you don't have the multipoint star spikes.

[laudropb]

Very nice wide field image. Thanks for posting.

[physicus]

Thanks for the comments guys.  Stardust: yes, I heard that too about stopping down at the front.  I might try a filter step-down ring for starters.  I'm not too fussed with spikes provided the fields not full of bright stars; and of course some folks put 'em in with software! I'd like to find the sweet spot at full zoom (400mm), not least because setting intermediate zoom settings between sessions is challenging (especially as the packing in my zoom-lock ring has departed over the years).  It just means scaling during stacking, but it's a hassle.  While I'm on, here's the same pic with some basic noise removal:

[Uranium235]

Pretty good mate, let us know how you get on with that TS adaptor (Im thinking of getting one meself), would like to know if there is any play/slop in it.

[ultranova]

very nice indeed, nice and contrasty.

well done

Paul

[tony210]

Great shot - love monochrome on this sort of target - best wishes Tony

[Stardust]

Oh yes filter step down rings, that's a good idea.

The TS- EOS-T2 is a good adapter but the Geoptic has filter threads 

[swag72]

A good field of view - LIke it

[physicus]

Oh yes filter step down rings, that's a good idea.

The TS- EOS-T2 is a good adapter but the Geoptic has filter threads

There are two versions of the TS adapter. The one I've bought via 365Astronomy has the 1.25" filter insert, and actually looks almost identical to the Geoptik. I looked to buy a Geoptik a while back, but nobody had them in stock; but comparing the two, there appears to be nothing between them. The simpler TS adapter is I think a bit thinner, but no filter adapter or 1/4 tripod fitting etc. If you fancy a Geoptik, shop around, prices seem to widely vary. Anyhow, if the TS is any good I'll let folks know.

Also, only just noticed how SGL mangles posted images. For what it's worth, here's a better version of the WIP

https://flic.kr/p/z6NDJj

Tim

[Stardust]

I had to get the thinner TS one for my Atik One as the Geoptic is too thick and wont work with that camera. I also have a Geoptic which I bought before realising it wouldn't work. My friend has it on loan with my 100mm macro on his Atik 314, I want to see the results with the idea of doing the same with a second camera, one day.

[physicus]

I had to get the thinner TS one for my Atik One as the Geoptic is too thick and wont work with that camera. I also have a Geoptic which I bought before realising it wouldn't work. My friend has it on loan with my 100mm macro on his Atik 314, I want to see the results with the idea of doing the same with a second camera, one day.

The tiny back focus is a great source of frustration for many. I can't quite squeeze my Celestron Skyris wheel in between my EOS lenses and the 460; the connecting pieces kill the deal, even with my home-made endcap mod - which itself is very efficient (without the wheel I need to add a 12mm spacer). So you can't win 100% at this game. I was successful with a large format camera lens, but it is old and suffers from bad CA, so is fine for NB but nothing much else. My other EOS is a 17-40 L, which, astro-wise, performs well on the DSLR - so I've great hopes for that as a super-wide on the 460. How you mount these lenses is another issue. The 100-400 has its own shoe, so the camera hangs free; I think you can bolt your Atik One down and have (a reasonably sized) lens hang off that. So I'll use the TS/Geoptik in two modes: its shoe being redundant with the 100-400, but I suspect a perfect balance/mounting point for the 17-40. At least this stuff keeps us off the streets!

[physicus]

The TS EOS adapter turned up yesterday, and I've tested it with the 17-40 L and 100-400 L zoom.  For the Atik460 I used a 11.5mm T2 spacer (think it came with my OAG) to achieve focus with both lenses.  I tested the arrangement in the photo on the sky last night and everything was good.  The TS unit is all metal, and the connections can be made rock solid with no play etc.; no orthoganality issues.  The bayonet locking ring is nice; the bayonet fitting itself quite lose with no springs etc, but the ring then 'pulls' the lens against the fitting as tight as you like.  It all comes apart easily too - which can be just as important !  I've been mounting the arrangement on the back of my C9.25 via a  Losmandy dovetail clamp.  If you get one of these, don't expect to accommodate a filter wheel - they're too thick - but I think some folks have accommodated narrow filter draws.  I've been fitting the individual filters through the lens end of the adapter, involving releasing the bayonet clamp and taking the lens or camera off (the 100-400 having its own foot, the 17-40 using the adapters 1/4" tripod fitting), unscrewing a reducer ring (or unknow thread size) into which the 1.25" filters fit.  A bit fiddly, but still doable in the field.  Drawbacks?  Apart from the fiddliness, it occurs to me that if you want flats that will catch dust motes etc in their in-situ orientation, it's necessary to take them as you go between filters - as there is no way to reproduce filter orientation after a session as you would with a wheel.