Stub Mandrel

Exactly. A La Palma M82 would cover nearly 100 times as many pixels... 1 arcsecond of sky to 19 pixels of my Canon 450D in fact! My 80mm by 1.2 m Mak is pretty much optimal for the 450D at about 1 arc second per pixel. Bin La Palma 19x19 and it will image a faint target a LOT faster at the same scale.... Interestingly the La Palma Liverpool scope uses a CCD with 15 x 15 um pixels - roughly nine times the size of those on the 450D and giving a scale of 0.45 arc seconds per pixel. To properly compare my 130P-DS with it, it's important to realise the La Palma scope is giving twice the image scale so double the detail, but as the f-ratio is pretty much the same it is catching more than four times as much light per pixel. Bin La Palma 2 x 2 and it will give more or less the same image in 1/19 of the time. That's even without allowing for the La Palma scope being mono with filters and slightly higher QE.

It should take longer to expose, but you get a much bigger image. Only if you use the same sensor. The myth buster is that if you image at the same scale, i.e. with great big pixels or much binning, the exposure needed will be a tiny fraction of that for the smaller scope. What would be really useful to astronomers would be a single number that covers aperture, focal length AND pixel size. This would allow direct comparison of the relative 'speed' of any scope+sensor combination

If you point both scopes at the same (large) grey card, the skywatcher would need a shorter exposure. http://telescope.livjm.ac.uk/TelInst/calc/

Hi Matthew - good start, but you should start a new thread for each image so it can be discussed individually. this thread is just to discuss the overall competition.

'76 was outstanding because it was such along, hot summer 4 months or more with barely any rain or cloud. A lot of hotter years/months since,especially from 2000, but now we seem to get hot rain... In the 90s, we ran a 'Dying of Thirst' campaign in the wildlife trusts because of the low state of many rivers and reservoirs. To launch it Prince Charles visited a cracked reservour bed, the heavens opened and...

'76?

The 64 bit DSS download link for windows is https://github.com/LucCoiffier/DSS/releases/download/4.1.0/DeepSkyStacker64Installer.exe The link on Yahoo and some other places is incomplete/broken.

How long a sub do you want? With a HEQ5 1-2 minute subs should be achievable at 600mm without guiding and excellent polar alignment.

The end loading of taper bearings is critical to their performance. For this application you need the absolute minimum of preload, just enough to make sure they don't come loose when you mount a telescope. I would suggest doing up the adjusting nut until all shake disappears and then just a tiny fraction of a turn, perhaps 10-15 degrees. <edit> with taper rollers in this application, I would be tempted to us no preload at all unless you can detect movement in use. Those taper rollers should NOT need replacing at any point in the lifetime of the mount, unless they get corroded. Those bearings arte big enough to take the loads associated with a good sized lathe and would be expected to last millions of revolutions under difficult conditions and heavy loads while keeping their basic accuracy. A telescope mount might make hundreds of revolutions in its lifetime.

Galilean optics Apparently this also means brightness is increased by magnification rather than focal ratio - which increases field of view.

I expect it was like Falcon Heavy with marginal fuel available I imagine they would have 'practised' until the fuel ran out then drop like a stone... I wonder if they managed to get the fairing back? The two second stage cameras were interesting. One supported a round earth, the other was fuel for the flat earthers! No doubt just different focal lengths. They did make a few pops at NOAA didn't they - Iridium is hardly the same as a spy satellite although there may have been something else on board ;-)

If they are using washers to set the clearance for a worm gear, they will almost certainly need to be selected to suit the individual setup - if they could machine it accurately enough to always need the same size shim, they could do it accurately enough not to need a shim... You can get thin shim in many materials and build up the exact thickness that gives you minimum backlash with no binding. I plan to do this with my EQ3 to replace the 'push-pull' screw adjustment.

Wahey! Well done Nige! We'll all bask in the reflected glory!

I'm 'badly conflicted' on the saving up front (1) I could do with a new set of wheels and (2) I just don't seem to be getting enough sky-time to justify the expense

Indeed, there are people who will pay £8,000 for a British lathe over an equally (more) capable and much more modern Chinese one for £1,500. Why? Heritage, finish and a few less rough edges. Generally these are people who put considerable weight on the pleasure of using a nice piece of euipment. Just as with scopes personal preference can spill, over into unwarranted criticsm. A major downside of this is taht beginners can be put off because they are told the cheap option isn't good enough, a fallacy as 'good enough' is entirely subjective.

What do professional astronomers use?

You could end up regretting making that offer to an ecologist

Don't fret @ollypenrice, I've fixed it for you (Alternative title: "What a Refractor Owner thinks Newtonian Users see")

I worry about the amount of 'gun' content on a website by someone who obviously has a chip on their shoulder. Virtually all 'x is better than y' arguments are sterile because the needs and wants of individuals vary so much. Let alone considering differences in sky quality, acuity of vision, colour perception, pupil size, time availability, local climate, budget, other equipment... I am totally of the view that the best equipment for anyone is something they can afford and find pleasant and straightforward to use. Very often someone's choice of viewing will follow the capabilities of their equipment and not the other way around.

Forgive the double posting but in case it's missed elsewhere this is last night';s effort, 3 1/2 hours of Ha subs on the EQ3, guided.

I find eBay is great for mass produced, inexpensive bits and bobs, especially things like little electronic modules or packets of 3D printer bits for 99p + a couple of weeks wait. Sometimes I will pay the extra pound or so for the convenience of not having to set up yet another account to buy something. I did that to but some cheap 1.25" filters. Sometimes I find I've used the same (professional) seller a few times, so I search out their website and but direct - this goes for some metal suppliers for example. For anything over a few tens of pounds (e.g. scopes and decent accessories) the 'proper' shops are cheaper and you get more confidence in warranties and customer service.

Live view is teh best way, make sure you zoom in and if possible get a bahtinov mask (a 'CND symbol' cut out of card works fine).

Yes I can see a doublet may help with that, but surely that doesn't require ED glass?

This is probably an unwelcome question, but why do you need an ED doublet for a scope that works with monochromatic light? You can't get CA with Ha.

Ha - brings how just how bloomin' enormous that scope is! I'd assumed it was was an ordinary one.