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pjmaciw

Do reflectors need dew shields

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go to hobbycraft and buy some sheets of 2mm black foam, either self adhesive or not and make one from that and join with velcro. works a treat.
That's what I did, except I superglued it and made it about 5mm less in circumference than the 200p so it's a snug interference fit. In time, I suspect it may slacken off, so I'll make a velco 'belt'.

I have had dew issues on the primary during visual use, but I must say the shielding it provides from extraneous light, however little. It is quite noticeable with lower power, wide angle EPs.

Russell

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You know,that was a perfect question!!! i did a post not long ago asking sbout things like that that i would need as i havent had my scope long, got a few repies but mainly saying i didnt need a dew sheild,i didnt need this......etc lol

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I think consensus is that it does no harm to have one, it might help with reducing dew on your secondary, and it will keep stray light out. BUT there is little bebefit to spending a fortune on one when with a cheap bit of camping mat / exercise mat / foam board you can knock up your own for a fraction of the cost ;-)

That's how I read it anyhow.

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ok sounds good, so if i get a camping mat what measurements would i use for my scope then.... its a skywatcher 130m. definately up for a cheap way around it lol

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Don't measure it, wrap it round the end of your scope, allow an inch or two overlap ( where you put the sticky back velcro) and cut. Cut out a notch for your focuser and finder so it can sit 6" ish onto your scope. Apply Velcro. I put it scratchy side up so only the soft side of the Velcro ever points towards the scope so I don't scratch it.

I'll put some photos up of mine later when I get home.

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I've just made one for my 8" using stiff black cardboard to form a tube which is then lined with black felt. Fits snuggly over the outside of the tube and gives about 12" extra length. Cost less than a fiver :)

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ok sounds good, so how much length have most of you got from the actual end of your scope, yours looks quite long russ.will. a few inch would suffice wouldnt it?

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Mine is also about a foot long. {Stop sniggering that boy at the back}. I have an explorer 200pds and the homemade dew shield extends about a foot beyond the tube. Seems to work adds little weight and is no problem for my heq5 mount.

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go to hobbycraft and buy some sheets of 2mm black foam, either self adhesive or not and make one from that and join with velcro. works a treat.

That's exactly what I did, much better and you can customise it for your scope. Or you could just use a camping mat?

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ok sounds good, so how much length have most of you got from the actual end of your scope, yours looks quite long russ.will. a few inch would suffice wouldnt it?

It's about a foot - the same length as the foam sheet. As that was already cut square, I couldn't see the point in complicating the issue by cutting it down further.

Russell

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the only time my secondary ever dewed was when I left the focuser empty with no eyepiece or plug in. the dew fell straight on my secondary. the primary has never dewed (other than when brought inside).

I am a new dob owner (10 inch). Scope was outside for about 4 hours from 3.30pm this afternoon (failing to see any eclipse evidence). The outside temp has dropped to about 2.0C now and I have brought the scope back inside where it is snug and warm (my garden office). Mirrors were clear when I brought it in, but within 3-5 minutes crazy paving condensation appeared all over my primary. I have blow dried it with hair-drier twice and it seems to have dealt with it. Mirrors clear now for last 10 mins.

Is this standard procedure - and the correct way to deal with this issue?

Thanks.

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for the first time ever at Peak Star Party, my 16" solid tube, fully flocked and with a dew shield dob dewed both the secondary and the primary. in fairness, this was in conditions which were basically like the middle of a cloud (very misty with mist literally falling down like extremely fine rain) and I stupidly left my scope at about 60 degree inclination for half an hour or so without moving it. I suspect that had I not left it turned toward the sky or capped it then it would not have happened but it certainly can happen I now realise. thankfully as you'd expect, the conditions were really not conducive to observing. the mist cleared off the scope about ten minutes after the air cleared and with a light breeze it was not long before all was restored to shininess.

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