Uranium235

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.

Fashionably late to the party Just booked, Fri & Sat night.

Behold... it's a miracle!! Three weeks this took (plus a load of chasing emails) But it's now "game on"

As for the mirror clips, there should be just enough room to slip a fag paper between the clip and the mirror... so get down the corner shop and grab a pack of rizla..lol

Sorry, I've been a bit ill the past few days. The veil shot was with the qsi 683 ☺ overall I was pleased with the field flatness on that shot. It did quite well over a 22mm diagonal sensor. I'll be firing up the 178 when I get my hands on the long overdue 135mm f2 lens. Been waiting over 2 weeks for it now... it's starting to take the Michael.

If you look closely at the corners, it will tell a story. The left side has normal coma (I assume youre using a corrector?), while the right is a different type of distortion (radial). That would indicate some tilt, either in the focuser, the way the corrector sits in the drawtube, or whether you have any loose connections. You might need to take time to square your focuser, simply tightening up all the screws doesnt quite mean that its pointing at the right spot on the tube wall. You have to remove the secondary and put in a marker for where the focuser tube should be pointing. There is stuff on youtube how how to do this, but I wouldnt attempt it until you have the bits required (digital calipers etc..) The stars in the middle are a bit so-so, but you didnt state whether you were guiding or not.

Its been a very long time.... perhaps too long..lol. 20x450 Ha on the Veil, starting off on something easy. No calibration either. I'll probably process it again later on when I remember what it is I used to do

If the FW is attached directly to the camera - the m48-T2 adaptor will be about 11mm. If you have a large format camera (diagonal of 22mm +l, I would use 36mm or 2 inch filters anyway. The shorter I make the mod, the more options the user has got to configure it in a way that suits their camera. ☺

I'm trying to keep it as close to the original distance of 44mm. But I can afford it to be up to 2-3 mm thicker (still leaves loads of room for a FW). I'm making the m48 thread just 4 or 5 mm. That way any extension ring or FW will screw right up against the lens mod if you so wish ☺

Still waiting for the lens... ughh this is like pulling teeth...lol

Still waiting for me lens! Looks like it's going to be a drop ship jobbie, so perhaps Wednesday or Thursday.

Well.... this is turning out to be a popular idea Ive tried the Geoptik adaptor, but i found it a PITA to change filters. The adaptor I have planned will allow the useage of pretty much any standard thickness FW (~21mm), as long as your camera backfocus requirement isnt ridiculous (like 20mm+).

Its alright Ive already seen the inner workings - a fellow SGL member was brave enough to take his apart so I could see if there are any nasty surprises lurking underneath the bayonet, and there isnt - so its all systems go

Im aware that the same rule will apply to any variant of the 135mm (and maybe other lenses - even for mirrorless), the modification Im proposing is about getting completely away from bayonet connections and moving it to a screw-fit. Those links seem to deal with the idea of switching between lens mounts of various manufacturers, which doesnt really apply to what im doing as im ordering a custom mount (focused on AP) from scratch. Of course, once its modded you wont be able to just pop it on your DSLR again - unless you take 10min to swap out the lens mount Lets concentrate on the 135mm f2 MF for now, get it working - and then we can take a look at where else this can be applied.

If the camera is modded (as in filters removed, but not replaced), the sensor may need to be re-shimmed to work properly with some lenses. I had to do it to avoid the hard infininity stop with the Samyang 135mm. Or, you can try using EOS utils to get a proper look at stars while focusing. Typically, a modded camera in my experience has a difference between what you see through the viewfinder, and what you see on the preview screen - the preview screen is the one that tells the truth (for daytime photography anyway).

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