alacant

Hi I believe that on this forum, we're not allowed to use the terms fast and slow for anything other than motor vehicles! If your target runs out of the field of view of the smaller sensor, you're going to have to move the camera and take more frames. Then combine them in software. That takes a long time. The large sensor get it all at once. No need to move the telescope and take more frames. If your target fits into both the small and large sensors' field of view and the sensors are of equal sensitivity, then it takes the same time to build the image. It doesn't matter what focal ratio you use. The only way you can get the image in less time in the latter case is to use a larger aperture telescope. Sometimes theory and explanation just don't help. When you've seen it first hand, you get it immediately. I too needed convincing. Try a side by side on the same target with a large and a small telescope. e.g. 80mm and 130mm. Markarian's Chain is a good target . Do 5 minute exposures in each. You'll not need telling which image is taken with which. Same exercise with a large and a small sensor, but same telescope. The whole of Markarian's Chain fits into one frame with a large sensor but you'd need say 2 frames to cover the same area of sky with a small sensor. Try with a 183 and a dslr. HTH

+1. Well said. Thanks for posting.

Can anyone share hands on experience with it? https://www.teleskop-express.de/shop/product_info.php/language/en/info/p49_TS-PHOTON-8--f-5-Advanced-Newtonian-Telescope-OTA.html Or any other non skywatcher 8" f5. TIA

Can anyone share hands on experience with it? https://www.teleskop-express.de/shop/product_info.php/language/en/info/p49_TS-PHOTON-8--f-5-Advanced-Newtonian-Telescope-OTA.html Or any other non skywatcher 8" f5. TIA

Hi everyone Stumbled upon this in kstars looking for something interesting whilst waiting for the mw to swing around. Lots of fifty threes. A proper globular cluster and a budget globular cluster. Despite the overwhelming distractions to the south in Scorpio and Sagittarius, I persevered until I just couldn't resist this new moon's challenge: m7. Alas, by then, it was getting light. I may just sit it out tonight on the southern horizon hoping for some decent seeing or -far more likely- set it going and throw away the rubbish tomorrow morning. Thanks for looking and stay safe. 700d @ ISO800

Hi Absolutely stunning. Love it:)

Hi everyone This time it's The Lagoon. I was a bit stuck as to the correct colour for this. Nothing new there of course, but easily solved by a quick google image search. The correct colour seems to be american-diner-garish with most of the stars removed! Thanks for looking and do please share your m8 images. 700d @ ISO800

Hi everyone The heat is with us once again and the galaxies are rapidly going west. Set the scheduler to swing over to Sagittarius after a foray into Virgo for m104 earlier but miscalculated the time the latter would take. Ended up with M20 an hour or so past the meridian with less than 2 hours before dawn. So with the excuses over, this was another step on the road out of the 1990's. This time with DarkTable. The masks are nice. Thanks for looking and do please post your versions of m20. 700d @ ISO800

Thanks for posting and please do report back re the blackening. Cheers

So do we. A lovely old reliable instrument. The newer sw stuff just seems to be thrown together. Cheers and thanks for your interest.

Sorry. Didn't include the link.

Unless you're on the having-to-sort-out-non-existent-skywatcher-quality-control end. LOL. It's not the first time I've banged my head against this. But it will certainly be the last! It's such a pity as it produces lovely images. So long there are only very faint stars in the fov. Even then... Cheers

Hi This issue was solved by cutting off the focuser tube which was intruding into the light path. The current issue is the pattern surrounding bright stars. Anyway, I've yet another secondary mirror on order from TS. If that fixes it, good. If not, time to give up! Thanks everyone for your time and patience.

siril

Just before I finally take the hammer to it... The spikes are the same with and with out cc and with and without filter. Cheers

Hi The pattern retains its relation relative to the diffraction spikes. Substituting the camera also results in the same image with the same spikes. It's only the 200pds which produces these pronounced spikes. Other Newtonians are fine. My conclusion to this test is that it's the telescope producing the effect, not the camera. Thanks

Hi OK. Here is Vega out of focus left and right and in focus left-centre-right.

Hi Peter, everyone OK here is an in and out Arcturus. Cheers

Hi. Yes. Blackened secondary edges and blackened main tube. I also blackened the dawn off part of the focus tube. No mirror clips. Running out of ideas! Thanks.

Hi. There are unsightly spikes no matter where the star is located in the frame. They are distorted by the cc toward the edge. Thanks.

I wonder. When I change the secondary, the spikes change too. Gonna try the out of focus star too. Thanks.

Grrr...Maybe I am! It's just that using many reflectors over the years, I've never seen anything as bad and pronounced as this. Yes. On the end of the focuser barrel where I cut it off to prevent it protruding into the light path. Blacken it? Cheers

Hi and thanks for your feedback. The secondary is 58mm and it looks as though it covers aps-c ok; there is minimal vignette. It's the same; 700d and 450d albeit more noise with the latter plus the 700d works spike free with both our ES reflectors, 250p and 130pds. Ok, there are spikes but not as pronounced and they are symmetrical. Thanks again.

Thanks. Yeah. perfect:)

I wish it were! OK, no clips and a sawn off focuser tube. Exactly the same awful spikes. Rotated the primary. exactly the same awful spikes. So it has to be the secondary, right? Take out the 58mm secondary from the old 250p and place it in the pds. In the dark. Shining a torch to get collimated. Looked in the light of day and the secondary was way off centre. Anyway, managed 8x3 minute frames and hey, different -but still awful lopsided- spikes... Here's hoping that with decent collimation, the spikes will at least get evenly radial. Just called TS (the only place who do sw replacement parts it seems) €90 for a replacement secondary. Wonderful. Really fed up with this telescope. Look at the spikes now. Still wrong... Ahhgghh!