Low tech focusser improvement for Maks (maybe SCTs too)

[Jove]

This was a discovery made 'in the field' ! I was trying to focus on Jupiter while a webcam was fitted to my Mak. Now, the focusser on the Mak is a bit of a pain as it is a knob poking out the back of the OTA that you twiddle left or right to focus. It is more or less impossible to move it without the vibration causing the view to bounce around all over the place, in the case of a webcam its very easy to lose the target altogether. Unfortunately, with a webcam fine-focussing is really important, so something had to be done.... inspiration struck in the form of a humble clothes peg! Attached to the focusser knob, the extra leverage allows for suprisingly fine control of focus and banishes image bounce while doing so.

Sorry, hardly DIY, but thought someone might find this tip useful!

[IanL]

Must rate as the cheapest focus fix ever!

The usual method is to get a plastic jar lid and drill a hole in the centre so it push-fits over the focus knob, or maybe use a small amount of glue to hold it in place, thus creating a giant focus wheel. Nutella jars have a nice knurled edge for extra grip.

[JamesF]

I used to use a clothes peg before I added the motorised focuser to my Mak. The clothes peg or the jar lid mod are probably the easiest and lowest cost ways to improve stability when focusing.

James

[Gina]

I'm looking into focussing my wide-field lenses. ATM I have the one camera attached to the dovetail with a ball and socket head and it's none too solid so touching the focus causes the image to wobble all over the place. It'll be better when I have a more solid attachment but I will still need a finer adjustment method. I'm thinking of either a lever or electric remote focus.

[IanL]

Gina, what type of lenses are they? From your comments I assume they must be manual focus only?

On the other hand, if you're using auto-focus lenses on the 1100D's, you should be able to drive the focuser through software. E.g. I use a 500D with the kit EF-S 18-55mm zoom from my old 300D and a generic Sigma 200mm zoom plus BackyardEOS. In BYE on the 'frame and focus' tab there are focus in/out controls with which you can drive the lens focus completely hands off for both of these lenses.

I plan to to build an ASCOM-compliant focus motor for my revelation crayford which BYE should also be able to drive (but before that I need to build my dew heaters, and figure out what is wrong with my guiding set-up, etc., etc.)

[Gina]

They're old telephoto lenses from film SLR days with M42 screw thread (Pentax/Praktica thread). Manual focus - in fact manual everything

[Stargazer33]

Excellent tip Jove!

I was using a large plastic ring on my old Mak but must admit to not using anything on my SCT yet. I have acquired a plastic ring from work that I hope will fit but then you still need two or three fingers to rotate that ring. I like the idea with the peg (lever) as you can change focus with just one finger so less vibration due to not actually having to 'hold' the focus ring!

Help yourself to a Jelly Baby for that one!

Bryan

[Stargazer33]

I managed to get a plastic ring from work - actually the receiver holder from a BOSE X headset that was scrapped - that with a little judicious reaming (!) I was able to slide over the focuser knob on my C8. I drilled a small hole in the side of it and pushed in a cut piece of a straw from a can of dust remover (spray air). This was glued in place with some epoxy.

The dust remover straw has been re-enforced with the ink holding straw from a ball point pen which luckily fitted inside. I cut the straws down so that they just pass the mirror diagonal.

Thanks again for the tip Jove!