Knight of Clear Skies

An alternative to using a filter wheel would be to attach a 2" filter to the front of the lens, using a step-down ring.

I've used mine wide open and at f3.5, here are a couple zoomable example images on Flickr. Andromeda at f3.5. The Pleiades at f2.8. These are unguided shots, so that could also have some bearing on the star shapes as well. It's certainly useable wide open but I'm still experimenting, the bright stars are a little messy so I suspect the aperture ring is intruding into the light path. I'm going to try fitting a step-down ring as a front aperture mask. Another thing I haven't tried yet is the lens tool in StarTools, to see if I can improve the corner stars. I believe the author of the 'Astronomers Do it in the Dark' site uses his at f3.5, from my tests I don't see the need to stop it down any more than that. Hope that's some help.

Some people have tried filling the EQ3 tripod with sand to make them more stable. There is also this thread on stripping down and tuning up the EQ3 which could be useful. Yes, I also think unguided imaging at short-focal length is a good and relatively inexpensive route into imaging.

Interesting thanks. That's a lot cheaper than Nikon infinity focus adaptors I've seen previously, I can't tell whether it has a glass element or not. Not sure what to think about that, whether the listing is incorrect, it has an element (and dodgy image quality) or whether it's a new design that manages to get the lens in the right position (I did a lot of searching on this but that was a couple of years ago now).

That's not the right adaptor then, the simple ones do work but don't reach infinity. Can still be useful for close-ups and macro work though. I tried putting an M42 lens on a friend's Nikon and ran into these issues, it took a while to find the correct information.

It's an old lens mount commonly used from the 1940s to the late 1970s, 42mm threaded. There are lots available on the 2nd hand market. I've used several for AP, here's some of my favorites: ...and here's my latest image from the 50mm lens on the left.

Yes, the do reach infinity using an adapter with a lens element, but they aren't cheap, it changes the focal ratio and can impact image quality. There are some good M42 primes lens that are available for around £15-£50 so this is a factor worth considering for lens imagers. (There are probably some good vintage Nikon mount lenses out there too, but I've never seen an image taken with one.)

Perhaps the difference isn't as marked these days, I don't know. I have APT which is a fantastic bit of software and cost about £12, I haven't explored it properly really but have used it for planetary imaging to grab data from the camera liveview. Backyard Nikon may be very similar but is more expensive and I'm not sure if it's out of beta yet. Historically Nikons have had problems where the RAW files aren't RAW enough (the Canon RAWs aren't perfect either), the in-built noise reduction tends to eat stars. I believe there is a work-around these days but don't know how well it works or how much hassle it is to apply. I also make heavy use of old M42 camera lenses which wouldn't reach infinity focus on a Nikon body. I keep hearing that Nikon has the edge for daylight photography these days. But is that because the sensor is fundamentally better or is it because the camera does more processing of the image? (I recently upgraded from a Canon 1100D to a 700D as my regular camera so I could have the 1100D modded. I noticed the images from the 700D come out of the camera with brighter colours, I can't help wondering if that's simply Canon tweaking the output to differentiate their models or genuine sensor performance.) Basically, they are all good cameras these days. Canons are well proven for AP, I'm sure good results are possible with Nikons too but there may be more limitations and hassle involved.

Glad you enjoyed your visit and nice job with the AP and painting.

Many congratulations Tom & Olly, richly deserved. I'll have to go down to Greenwich sometime to see it in person, the exhibition runs up until the 26th of June. I wonder how big the printed version is?

The "Build the Milky Way" magazine is the really expensive one.

Good luck putting your widefield rig together. I can get 2 minute subs consistently at 135mm with my EQ3-2, there are a few images I've taken with my rig here if you are interested. If you're on a budget there are some great 2nd hand M42 lenses available.

Unfortunately not, I think because calibration of all the different cameras in Android devices would be a nightmare.

I've had readings in the low-to-mid 21s when out imaging at Caradon Observatory in Cornwall, with a high of 21.6 IIRC. There was one report of a reading in the 22s there but that was a one-off - I can't find a link now but I've read that the meters tend to overestimate once they hit the high 21s.

Don't suppose there is any news on the museum project Olly? This really deserves to be seen by the public.

That's a wonderful effort Tom & Olly. Would love to see it in its full 8 meter glory, best of luck finding a displayer.

It's really encouraging to see what this scope is capable of and it's something I'll consider further down the line.