Very exciting day today, picked up my Skywatcher 180 Mak. Of course, it's now cloudy in Melbourne...
I've got it on my Vixen Super Polaris, which I think will just handle it for visual. It balances well, but with both counterweights at the end of the shaft.
I've got the stock 28mm 2" skywatcher, and also bought a Saxon SWA (68 degree) 13mm, and borrowed a 10mm plossl to play around with.
Thanks to everyone who offered advice in the beginners equipment forum. I'm really happy with what I've ended up with.
Wavytone has described in another thread an excellent way to reduce thermal and dew issues. By using a yoga mat or similar, an insulating layer can be fitted.
I also have some 1cm thick carpet felt/underlay, and was thinking of adding this as well. It could go in between the scope and rubber yoga mat.
Does this sound like overkill? It would add a few hundred grams but this shouldn't be an issue.
I've followed Wavytone's suggestion and made up an insulating cover using a yoga mat. I added an extra step and did a layer of aluminium foil shiny side down before putting on the rubber. I figured if it reflects any heat back into tube and so forces more through front corrector this has to help.
(It will most likely have no effect at all, but I have an obsessive streak...)
Also, I'm thinking of leaving it on permanently (or at lease long-term) so if the rubber perishes at all there will be at least a tiny bit of a barrier protecting the tube.
Trying this idea myself. I've used some foam sheet as they use for packing stuff in. It's closed cell about 10mm thick. My Mak lives in the Ob so cool down is not much of a problem but if I can mitigate dew I'd be very happy.
Wavytone, do you leave the rubber on your scope all the time, or just when in use? I'm wondering about mildew forming, as there was quite a bit of condensation on the tube when I removed the rubber the day after trying it out.
On another note, I've read of people fitting a crayford-type focusser. Has anyone done this? I'm not used to the focusser on this scope yet, and am still finding it a bit difficult. I feel like can't get a fine enough adjustment. It could be my technique.
I only fit the insulation when assembling the scope.
Moisture attracts mould so it better when packed away to have the scope bare and in something that breathes (canvas).
On the SW I thought the focusser is fine. It’s possible to add a Crayford but frankly I never saw any point in it.
Fitting a Crayford requires more backfocal length. The result is that more light is cut off by the diameter of the hole at the back of the scope (can’t change that !) so you end up with slightly more vignetting.
Another thing to understand is how much magnification you’re working with in these scopes, and being f/15 the focal plane isn’t so sharply defined as it is in say f/5 scopes. Those coming from fast newtonians or refractors will take a while to get used to this.
Conversely put a big 2” 40mm eyepiece in and sure the focus will snap just as it does in a dobsonian. But bear in mind most users of small dobs probably don’t go past 120 or 150X most of the time. With your scope, the fun really starts at 200X.
Thanks. My last scope was a newtonian so it is a different feel. I'm also trying to get used to the image shifting when adjusting focus. With Saturn in the eyepiece at around 200x, it moves quite a bit when adjusting focus. Imagining the image as a ball, it'll move one or two of these diameters. Is this normal?
That’s a bit sloppy, the image shift in mine was negligible - I mean, you could see a slight lateral movement of a fraction of Saturn’s diameter but nothing to be disturbed by.
Personally I’d leave well enough alone - these scopes are not something you’d can “improve” with DIY efforts.
strange I have not had mine dew up or show any issues. I usually place it outside and start using it. Same with my ETX. But I keep them close to where they will be used and so maybe they are well adjusted.
Like the SCT's the mirror moves up and down the baffle tube while changing focus.
The "slop" can be reduced by running the focuser in/ out through the full travels a few times to redistribute the grease (and reduce the "gap") on the baffle.
If the OTA is left close to the focus for any length of time (thinking about those fitted with rear Crayford additions) the grease film is reduced in this location and can result in more "slop"
