Pleiades M45 with Pentax SMC 135mm f/2.8

This is 28 images stack and 2 darks all averaging 5-8 secs each . Mainly I was testing the 135mm f/2.8 with camera on a tripod just to see how well it handled . I thought it did well .

How is using manual focus lenses with their hard infinity focus stops? I lost one stack of shots because as the lens was cooling down the focus was shifting.

AbPho wrote in post #17393119
How is using manual focus lenses with their hard infinity focus stops? I lost one stack of shots because as the lens was cooling down the focus was shifting.

What caused the shifting ? Did you bump your tripod or camera ? The MF lens i have are snug so i have no problem with shifting . But also too it's a prime lens , not a zoom lens .Also being an older lens the Pentax SMC 135mm f/2.8 has a builtin hood so that may account for the snugness . But the lens is tight . I use a Canon adapter for PK lens attachments . Here is the same at BhPhoto but i bought mine on ebay over 13 years ago . They are very good lens if you can get your hands on one . As far as focus to infinity i just adjust all the way to infinity then slightly back off , take a test shot and if the stars are good focus i leave alone but if out of focus i'll refocus , really simple .

http://www.pentaxforum​s.com …ax-A-135mm-F2.8-Lens.html

Ron: nice and which Pentax is this? Takumar 42mm mount or PK?

AbPho wrote in post #17393119
How is using manual focus lenses with their hard infinity focus stops? I lost one stack of shots because as the lens was cooling down the focus was shifting.

That is the exact reason you should never use AF for astro. This is probably one of those rare occasions where Manual Focus lens is as good or sometimes better.

samsen wrote in post #17393579
Ron: nice and which Pentax is this? Takumar 42mm mount or PK?

That is the exact reason you should never use AF for astro. This is probably one of those rare occasions where Manual Focus lens is as good or sometimes better.

Not a Takumar , it's a Pentax PK mount like this one : http://www.pentaxforum​s.com …ax-A-135mm-F2.8-Lens.html

I was not using auto focus. I said the focus shifted through the range of images for the stack. I assume it was from the lens cooling down to -27ºC from +15ºC (inside the car). Once I noticed and readjusted the lens was fine for the second stack of 49 images.

What makes infinity focusing difficult is the lack of hard stop. Celestron mentioned that he backs off from the hard stop. That tells me critical manual focus is still required even with those lenses.

is this the subaru constellation?

Deepsiix wrote in post #17393894
is this the subaru constellation?

Pleiades is M45 . Not considered a constellation . It's the closest Open Star Cluster to earth : http://en.wikipedia.or​g/wiki/Pleiades

Deepsiix wrote in post #17393894
is this the subaru constellation?

Celestron wrote in post #17394048
Pleiades is M45 . Not considered a constellation . It's the closest Open Star Cluster to earth : http://en.wikipedia.or​g/wiki/Pleiades

Good question and short answer: Yes.
But as Ron said, it is not a true constellation but more like cluster of stars.
Here is Ref to nomenclature Subaru that by the way is one the best cars ever build and I can certainly can say that because currently own two of them.

Subaru constellation Origin

But how I really remember them is "Seven Sister"
LINK
Or
LINK
Or
LINK

And even more interstingly are the stories that goes about these sisters that is beyond the scope of this thread and anyone interested, do a Yahoo search (Avoid Google that steals/collect your personal data for sale to third party), and see what you find.

Thanks for bring up the question.