Brand new 180 Mak

[morls (Stephen)]

Thanks Ken. Done it now, there are about 35 turns. Fingers crossed this will smooth things out.

[Bushy69 (Justin)]

Hi Stephen,

I added a Crayford 10:1 focuser and found it to be very useful for both visual and AP.

http://www.iceinspace.com.au/forum/a...3&d=1520994088

Just my 2 cents.

Justin

[ZeroID (Brent)]

Originally Posted by morls

Sounds good Brent.

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 turned up a 70mm dia ply disk and drilled a 22 mm hole in the middle. Slid it onto the focussing knob. Makes it a lot easier for finer control although I also find it pays to always focus from the same direction ie from too far in back to focus. If I go past it ( too far out ) and come forward it is not consistent with position. Half a turn in then slowly back out again.
I have my 2" flip mirror in between the scope and camera. Visual check option which is very useful for centring on target.

[morls (Stephen)]

Thanks Justin and Brent,
I've spent some more time with the scope, and I think I'm going to persevere without any mods. After doing what Ken suggested, there was definitely an improvement, so maybe it needs to be run through full range every now and then.

I also picked up om your point Brent, about the direction of focus. When changing from in to out, or the other way around, there is an initial shift that is quite significant. However, if I continue in the same direction the image shift is minimal, and not a problem.

I've only done this with the stock eyepiece (26mm I think?), so things might be different at higher mags. I've got an 8mm and 15mm Starguider Dual ED coming in the post, so they should be fun. I think (hope) they're Astro Tech Paradigm clones. At $70 each it's not too expensive to find out how they go.

[ZeroID (Brent)]

Hi Stephen,
I gather it's called mirror flop, thread play in the focussing mechanism. My ply disk is hardly a 'mod' but it does make focussing fine control a lot easier. I've also put a black mark on the disk so I can eyeball it's position better, makes it easier to relocate the sweet spot.

I've also added a small fan from a PC to the foam front light shield. It blows very gently ( 5 volts in a 12 volt fan ) across the front lens and seems to do wonders for the dew. I run 5v and 12v to the mount for accessories etc with a distribution box with 12v-5v selectable. The fan is only about 30mm in size and is hot glued into a hole cut in the shield. The foam mounting also stops any vibration transferring to the system. Was very effective last night.

[Merlin66 (Ken)]

A large Vegemite lid with a central hole to fit the knob works very well and the knurled edge is neat
(Also very handy to improve the stock focuser on a PST....)

[ChrisV (Chris)]

Buy up on the Dick Smith Ozemite before it disappears ...

[morls (Stephen)]

Originally Posted by ZeroID

I gather it's called mirror flop, thread play in the focussing mechanism.

Hi Brent, I just found this explanation of what's happening...I'm still considering adding a focuser.

Image shift, sometimes called focus shift, is different than another problem sometimes seen in SCTs, namely mirror flop. This occurs when the primary mirror tilts slightly as the telescope tube itself is moved, especially if it's moved through the meridian.