Uranium235

Oh, and ive just checked the technical drawings for the 683 camera... it appears the filter is ~20mm away from the sensor surface. Hmmm.... it might work, worst case scenario would be that I have to take it down a few stops to correct any vignetting from the filters.

Only the first couple of minutes are relevant for this, but even getting the bayonet off seems like a bit of a pain.

Ive just looked at what it takes to disassemble a typical canon (200mm) lens - its much more complicated, but not impossible. Like I previously thought, the engineering involved would have to be bang-on for it to all go back together as it should:

Things just got serious: Not sure how its going to cope @f2 as the QSI has 1.25" filters, wont know until I try it I guess.... but I've found the camera has a photo screw hole on the case, so ive just bolted it directly to the dovetail bar. The lens mod takes care of everything else, no need for further support EDIT: Actually, I can test the illumination/vignetting later tonight - I'll just set the lens to infinity and take a few flats, that should tell me roughly whats what.

The canon 200mm bayonet seems to be held by 4 screws. But whether all the electronics come out with its removal is unknown. With that in mind, the engineering would have to be precise. I need to see one in bits tbh.... but I dont think anyone is that brave...lol.

Yeah, the lens mod at the moment is only suitable for manual Samsung lenses. Canon autofocus lenses have electronics in the way, which might make disassembly and modification difficult (the Samsung can be modded by a monkey it's that easy). I'd have to get my hands on one and take a closer look to see if its possible.

Im just waiting for the dust to settle being as the SGL star party was cancelled. Then I'll ask FLO about getting a small production run sorted., maybe just kick off with 10 and see how we get on.

Oh ... no... I was hoping that this would be my only break in the run up to xmas gutted.... Oh well, cant be helped I suppose! Safety first, even if it was open I suspect a number of the roads will be impassable as well - Ive already had a couple of dodgy moments on country roads here in Worcestershire, I waited for someone else to try and drive through the flooded bits first before trying (very carefully) with my little car

Clear tonight, so time for more testing.... 46x240 on Andromeda:

Hmmm interesting reading! I guess this could (in theory) apply to mounted filters since it takes little effort to remove one from its cell and flip it over. Might be something worth trying if you are getting large halos on your particular setup - I wonder if this applies to narrowband filters? (probably not, but its worth asking)

Could you please point us to a link (reversing Baader filters) where this information is posted? Otherwise it means that 99% of all imagers have been doing it wrong for many years (including myself), as practically every optical system requires a flattener or reducer for imaging

Rolling shutters are a feature of interline type sensors, and shutters are used for full frame transfer sensors. Its all about the speed of which the image is read from the sensor (interline = fast, full frame = slow) http://www.optique-ingenieur.org/en/courses/OPI_ang_M05_C06/co/Contenu_07.html http://www.optique-ingenieur.org/en/courses/OPI_ang_M05_C06/co/Contenu_09.html

But, to really test it I need to use the KAF8300 camera - and try and get the same performace Ive had previously. Note to self: Get a finderscope....lol

Mod seems to work alright slightly better spacing and more diligent focusing required (ie: 2/3rds focusing). But, for just two hours - it aint bad I guess

Really, to get the best out of the lens you have to get the spacing to it focuses as close to infinity as possible. In the end ive had to add a whopping 4mm to the spacing to get it close (with a filter), without a filter it now focuses exactly on infinity.

Im hoping to test it tonight, partially cloudy but thats close enough for me...lol.. Still not sure on the spacing, Ive left it 0.5mm short for the moment and will add delrin spacers if required.

Starter for 10...lol

Yay! Scumbag College

Ohhh yes..... Its done. Pro job, and hopefully soon to be commecially available if there is enough interest: Oh btw, the tripod mount for the lens cost me something like 12 quid... amazon bargain...lol. It just needed padding out with some sticky back velcro and its pretty snug now. The whole arrangement is now simplified to screw fittings, and its rock solid.... no droop.

Measuring fwhm on one star only measures it for that particular area of the corrected field. You need to take the whole field into consideration when focusing. That's why it's a bit of a compromise at times

The corners on the pacman are much improved. That leads me to think that the focus can be tweaked slightly to improve the overall field. One thing I used to do is use a ROI box on the offending corner (for quick loop), take an exposure, then tweak the focus very slightly.... "are the stars better or worse?", if not, go the other way... if yes - check the other corners to see if youve knocked anything out of focus - if its still good, youre ready to rock. Sometimes its bit of a compormise. It takes a bit of time to do, but its worth it.

The right hand side of your images displays out of focus stars. This also corresponds with the master flat you posted earlier. Whether that is due to droop in your imaging train, I dont know. But an idea would be to test the lens on a DSLR and take some flats with that - if you get the same vignetting pattern, it will be the lens. If not, then you need to look at the way its attached to your astro camera as to what is causing it.

Update on the lens mod: Should be a week, maybe two at tops. Once its back I'll have a better understanding of how much spacing Ive got to fill. I want it to be as close to the infinity stop as possible (in order to get the best corrected field).

Might be worth upgrading to the ccd cls filter. It has a harsher cutoff and slightly better transmission.