yuklop

I really enjoyed this challenge and approached the challenge as setting myself the lofty ambition to mount a 50mm lens to my Atik Horizon Camera. I spent a few hours carefully crafting a mounting method out of the various adapters, found it wouldn't focus, so crafted another that seemed to focus far away in the day time. At night though, it turns out it wouldn't quite manage focus at infinity. So I had to very quickly hack it apart and use a glue gun to glue the lens to a M42 spacer ring. Then with some fiddling it worked. Oh, and it was held to a dovetail with electrical tape. After the initial construction there wasn't a clear night in about 8 weeks in Southampton, but Thursday night was clear so I went and took a couple of pics. All I could manage was about an hour on M45, then an hour on both an Ha and OIII filter on NGC2244. There was a load of tilt, and other artifacts, but I had much fun with my fantastic contraption, and the results are below. Maybe we'll have another clear night in Feb, and if that is so I might make a better mounting solution that perhaps allows me to mount any old lens with any mounting as I have a few random old manual lenses. That'd be nice, and SGL, fantastic challenge, I'll look out for future ones - I don't usually image much, so it was quite inspirational! Thank you. M45, 200 x 10sec subs. Full image had more artefacts than the British Museum, so a hefty crop happened. 40 x 1 min Ha subs + 60 x 1min OIII subs. Med Gain.

Oh, it has been a poor show. I saw the nifty fifty challenge and thought I'm up for that. Spent a happy hour working out how to tape a lens onto the front of my horizon mono, and it's been clouds ever since. Competition is open to the end of Jan I think. Be lucky to get a single sub by then at this rate!! It'll need extending.

I finally got the hump with my old Vixen / Orion dovetail not fitting on my larger mount with a 4 inch dual saddle. I was going to mount a homemade Losmandy bar under it, then realised if I put that on, it would no longer fit on the Sky-Tee. If I was loaded, I'd buy more Losmandy saddles or more vixen dovetail bars but what I lack in cash I make up for with an angle grinder. I guess this is cast iron, as it was a right resistant swine. Whatever it is they should make bike locks out of the same material. Looks a bit of a mess, but it works just fine. A bit of Brasso and it'll be good as new.

A FC-100 Classic. Its a superb luxury item. The standard by which I judge all other telescopes that come and go. I have the matching original focal reducer to go with it if I ever want to take photos.

The C6R is pretty good for the planets too!

So its seems this isn't a question without the answer anywhere online, so I'll post it here in case anyone else ever runs into the same issue. I asked Takahashi and they said 83.5mm. Helpful folks they are. They also said that their new fc-35 reducer would work better with modern cmos cameras. I am sure it would, and I'm sure its superb, but its quite expensive, so that's one for another day. In the meantime some analysis on the old original fc-100 reducer. It is a fantastic chunk of glass, with a 60mm clear diameter and weighing 366g. I ran my own measurements and got the result below by using the relationship that focal length in mm = (206*pixel size in micron) divided by pixel scale in arcsec per pixel. Plate solving gives the pixel scale. The graph below shows the results and inserting 590mm as the desired focal length (for f5.9 reducer on 100mm scope), the calculated backspacing is 83.572mm. A pleasing if probably unnecessary confirmation. The question that remains is whether or not it is any good vs a modern system. To my eyes a full frame looks great at all the tested spacings. Siril's aberration inspector takes a close look at the corners. They aren't bad. Best at a range around the optimum length. I compared it to a modern imaging rig using a ES80APO and a 0.8x reducer and it compared favourably under pixel peeping conditions with both setups showing similar amounts of distortion (the distortion with slight comet shapes pointing inwards to the centre). The tests were done with an Atik Horizon 4/3 sensor in both cases. I tested the FC-100 scope with no reducer and that has a slight distortion with the starts smeared perpendicular to an imaginary line pointing to the centre of the image (apols I forget the names of these distortions, perhaps someone can chip in below...). The final observation is that the 83.5mm backspacing is good compared to many refractor reducers at 55mm. The FC-100 back is M72, so a M72 to whatever you want (e.g. M54 or M42) is ideal for making most of that back spacing. With a 2'' nosepiece that I use into the Tak visual back that 83.5mm disappears quick, and doesn't leave space for my SX OAG and wheel. Best go buy yet another adapter I suppose. Hope this is useful to someone one day!

Hi All, Hoping an expert on here has some idea of the backspacing of the tak f5.9 reducer for the original FC100 (image attached). I had a go at trial an error last night and realised that was a fools errand. I'd guess the spacing is too large as I get comet shaped stars in the corners. Anyway, help greatly appreciated. Is there way to determine correct back spacing in the daytime? It was cold last night! Dan

You are spot on. The details of the mount are in this thread:

Hi All, I have a fantastic old telescope shown in the picture below. Its does a great job, but it is 31kg, and as such one can't just whip it off the mount and use shorter focal length OTA's on a whim. I used to really enjoy experimenting with different OTA's. So I really want to mount a second OTA, e.g. a 4'' refractor for wide(r) field views and the odd photo. I could try and piggyback it on the Cass, but that adds even more weight, and even more counterweight. What's your thoughts about mounting a second scope on the counterweight side of the mount, so it effectively acts as a counterweight itself. Or does that result in balance hell? Anyone done something like this before? Thank you. Dan

I have signed. Security lights are daft. They use energy, and help crooks see what they are doing. I am lucky enough that my fence blocks the light show from the flats at the end of the Garden, and I spoke nicely with my neighbours and managed to get theirs turned off. Our neighbours on once side had lights that were not well shielded and shone about 1,000,000 candela straight into our bedroom window! They were pretty good about it when that was pointed out. If you see the effects of the lights in your bedroom, you have a stronger case I think. Otherwise, you'll have to make your own light shield if possible.

No problems there. Its an ONSTEP system so I can change the steps per degree to account for any changes to the worm drive.

I have a very nice old mount. It does struggle a bit with guiding even small scopes. I also want to use it with a really heavy telescope, est 35kg worth of OTA. I have tried that telescope on the mount before and it works, but it didn't last too long before the cork gaskets were split. I changed those to PTFE gaskets, and these work better. Trouble is, I can't find suitably sized needle thrust washer bearings. The mount shafts are 1.5inch on Dec and 2 inch on RA. One of the RA bearings is 2inch shaft and a 7 inch surface. I have found these: Search Results: needlethrustset - Simply Bearings Ltd These are not very wide though, so although they would fit around the 2 inch shaft, they'd only use 3/4 inch of the surfaces. So do you think changing the PTFE gaskets on this mount would benefit me. There are 3 gaskets on each axis, one each sise of the work wheel, and one at the base. Should I change all of them, or would changing just one be enough to benefit from reduced sticktion, even if the weight was still tricky. I'd also like to change the worm wheels. The ones on there are 4.5'' and 7 inch for RA and Dec, but they use a very small worm. A larger one would likely be more precise. But I think that is an expensive job and likely one for later. Anyways, any thoughts or inputs are welcomed.# This is the mount: Dan

Love it. Its so very British! I'm thinking of all that American Space X, Blue origins, Kennedy space centre stuff, and then see this image, and think... how wonderful it is to be a plucky Brit, achieving useful stuff on a sub-1% budget. (At least next time, I'm sure they will do something useful). Go Skyrora.

I recently replaced my monitors. Got a 34'' ultrawide at 1440p. Its very good indeed, especially for astro editing. Can always make use of the extra screen real estate. 4k at that size would require a better graphics card, and that gets expensive. Specifically, this one: https://www.cclonline.com/90lm06f0-b01170-asus-tuf-gaming-vg34vql1b-curved-gaming-monitor-34-inch-3440-x-1440-uwqhd-va-panel-amd-freesync-black/?cq_src=google_ads&cq_cmp=13175109251&cq_con=125042006760&cq_term=&cq_med=pla&cq_plac=&cq_net=g&cq_pos=&cq_plt=gp&gclid=CjwKCAjw3qGYBhBSEiwAcnTRLnM3dXBpo2ihMqOcscI8VMeGvo3ibcADK1Ujlqj4T_x6KLkUN6K-ehoCOkMQAvD_BwE Although of course, I spend too much spare change on Astro stuff... so got mine second hand for a lot less than that. Defo consider an ultrawide if you have space though.... highly recommended.

Agree with the above. I had a LX200 12'' for quite a while, and had a lot of fun with it. Cooldown took ages though, even when stored in an unheated garage. At least 90 mins. Which meant most of the time I was using the thing unstabilised. I also felt I spent half the time collimating, and the other half wondering if the collimation was out. In truth, I was probably trying to collimate before the scope was properly cooled. But kids, work, and weather conspire to keep my observing between about 20:00 and 22:30. Barely enough time to cool it down. Sold it a while back. Do I miss it? Not really. I think the scope was a lot better than my skills, and at a different stage of my observing life, I'm sure we'd have gotten on a lot better. Would like to try a C9.25 one day. Would also like a decent refractor one day. But that's for the future. I'm presently messing around with a classical cass and a DK that I somehow ended up acquiring with more-or-less wise auction site bidding. First impressions are that they are sharper than the SCT, and easier to collimate, but they are also both open tube, and so cooldown is quick.