[Wavytone]

Hi Josh,

I've had one of these before (and stripped and refurbished it). They are small enough that you won't notice tube currents and there is no cool-down time. If you look very closely at the reflections in the front meniscus it should be a doublet lens - two perfect menisci with the tiniest of air gaps. All up about 3cm of solid glass up front.

Mine also cane with a screw-on dewcap extending another 12-15 cm out the front and with this fitted I never found any problems with dew. If the scope has been a bit warmer during the day it should take many hours for all that glass to cool down to the dew point.

The mirror inside any mak should never dew and that isn't the place to put heaters. Where a Mak can sometimes dew is the front of the corrector, when the front surface cools below the dew point. But these things have such a massive amount of glass up front that if it was warm to start with it shouldn't dew over all night. If you are really really determined to add warmers, I'd unscrew the front (it comes off easily) and fit insulated nichrome wire around the inside of the tube just behind the corrector, and bring the wires out through a small hole in the side plugged neatly with silicone glue.

If you are having focus problems its mostly likely the helical focusser is sliding slowly under its own weight with time - that is quite common if it has the original icky grease. A simple way to stop it moving is a piece of gaffer tape around the helical focusser, then fine focus at the back of the scope.

I modified mine for visual use, as follows.

If you unscrew the front part holding the corrector off the back half holding the primary, carefully look inside and you should see a screw protruding in from the side about 1 cm which is the infinity-stop for the helical focussing thread. If you retract or remove this screw it will allow the lens to focus past infinity a tad, moving the secondary about 1 mm closer to the primary. This has the effect of giving you another 1cm of backfocus to play with out the rear of the lens, just enough to accommodate a star diagonal and a 1.25" telescope eyepiece. You can also use this screw to lock the focus into position by screwing it in gently. This screw is hidden under the outer ring around the barrel that has the tripod screws set in it. To remove this ring, you will need to remove the rear mirror cell cover. This mirror cell cover screws off easily but take a very close look at it first as from memory there may be some tiny setscrews locking it in place.

If you do take the front off, when reassembling it take care not to get dust inside, nor get grease on the corrector or mirror. In addition, it takes some patience to get the helical threads to re-engage all round. For lubricant you can use ordinary vaseline.