Differential flexure and cheaper 'scopes

[arad85]

Hi all,

I'm just on the verge of starting to image with my EQ6. All I need is a few hours to put together the power supply now it's all been ordered and I'll be away.

I'm thinking of all the possible issues I may have, and the one I keep coming back to is flexure (I know there are lots of others, but from the engineering side of things at least). I don't yet have my guide scope, but I'm thinking of an ST80. My main imaging 'scope will be the C80ED and they will be dual mounted with one of Milambers SGL dual mount bars together with tensioner plate. Imaging camera will be the unmodded 450D, guide camera the DMK21.

I guess my question comes down to whether I should be looking at getting imaging/guide scopes with more sturdy and better focusers to avoid flexure there or are the ones on the stock 'scopes up to the job? Options include:

• Just get a ST80 and be done with it - it will be fine (cost £90)
  
• Get an ST80, mod it so it has a fixed focus point to remove any flexure there. Possibly then upgrade to a moonlite focuser for the C80 (cost around £350)
  
• Get an ST80 and sell the C80 and get something like an Equinox 80 Pro (cost about £400 once C80 sold)
  
• Go the whole hog and get Equinox 66 & 80) and sell the C80ED. At a guess around £550 all in once the C80 sold.
  

Whilst I realise I could just do each step incrementally (in fact, I'll start unguided...), that would cost more in the longer term.

What do people think? Would I notice much difference in the images in the steps above or should I just get out there and practice and take it slowly (I'm generally quite impatient :))?

Thanks

[johnh]

Hello, I would take it gradually as some of these issues will not occurr as every setup is unique and never 2 the same even with the same gear. I see you are eager but don't waste money on stuff you may not need. Getting a good saddle is vital and good quality rings and at low guiding/imaging fl these problems you highlight will be much less. It is having to use an extension for your DMK to get focus that can cause slop you don't want but you may not need an extension with ST80?

Getting 2 scopes you can image with both, image with one and guide with the other either way, one very short fl for really wide stuff and one significantly longer fl perhaps a bit larger objective 90-100mm for more resol'n.

Take it slowly and enjoy your imaging journey, you may find it easier than you imagine. Best of luck.

JohnH.

[Parallax]

I've got the ST80 alongside the C80ED on a HEQ5 Pro mount and haven't noticed diff. flex. (I did when I had the Explorer 200 instead of the C80ED). 10 mins guided subs are no problem.

Although I have to yet try it with the 1000D, I would say that the weight of the Atik 16 plus FW is comparable and everything seems to cope OK.

One thing I would say is, when you have focused the ST80, lock the focuser with the screw. Same goes for the C80ED I suppose, but I have fitted the SW autofocuser and tend not to bother (read: forget!).

Steve

[jgs001]

I'm in the same position as Steve, although I've modded the focusers on both the ST80 and C80ED with the judicious application of teflon tape to remove slop in the draw tubes. To give some idea, on the ST80, with the SPC900, I used to get sufficient movement in focusing with a 2x barlow to nearly move the target off the edge of the FOV. After applying the tape, I get so little drawtube slop that even with a x5 barlow the target remains in the FOV, it moved a little bit, but not enough to notice. I need to test out the C80ED mod, but so far looks good. Prior to sticking it on, there was visual movement in the drawtube when pushing and pulling up and down, now it's gone. The same is true of tightening the lock bolt, I used to see the adjustment with the 2x TC and 450d on the moon, not anymore. Without the focusser mod on the C80ED I've managed 20 minutes subs.

[arad85]

OK - thanks guys. Looks like it will be concentrating on the processing rather than the mount for the moment

John - any piccies of the mods you made?

[jgs001]

I'll see what I can do.

[arad85]

Ta...

[Starjumper]

I have the same scopes and would also be interested to see the mods.

John

[jgs001]

Guys, as promised... Bear in mind my ST80 is actually the Konus Vista 80s, but it's basically the same thing...

The Konus (it has 4 sets of strips following the felt lining in the focuser)

The C80ED (just a pair of sets, in line with the runners in the focuser)

The tape costs about £10. I couldn't justify spending twice as much on a focuser for the Konus as the scope cost, and can't afford the Moonlight that fits, and at the mo, can't afford the Agena converter and a cheapy crayford either ...

[arad85]

Very Heath-Robinson ... Where you get the tape Places I've seen are charging 4x that....

[jgs001]

I got the second lot (used on the C80ED) from oven liner, mouse mat, teflon tape, teflon tapes, uhmw tape, mouse mats, baking sheet, zone tape, oven mesh, baking sheets. The first lot (on the Konus) the shop no longer appears to be operating.

[arad85]

Great stuff John - ta

[ollypenrice]

Have to say that the ST80 I use for guiding has no flexure issues at all. I feel the lock screw jams everything up tight. I lock it down hard, something I wouldn't want to do on an imaging scope - and anyway doing so would mess up focus each time so there your teflon is a great idea.

Olly