My first dip into the cosmos - advice appreciated

[stevetynant]

Hi everyone - my first real post to the forum and as you will see a complete newbie to the hobby. I've always enjoyed outside activities - most sports, surfing, hiking, photography and birdwatching but want to try something new.

I've read a lot (never enough I know) and decided to take the plunge and am expecting the Skywatcher Skyliner 200p Dobsonian in the next few days from FLO. I've bought a Colimator, a 2 x Barlow and another eyepiece 7.7mm so pretty much blown my (wifes) budget already but I thought I'd rather get off to a good start in this hobby and if my interest continues over the next few years then expand (I'd love to do AP but obviously Its a long term project bearing in mind the costs - but kids nearly through college so perhaps in the not too distatnt).

Anyhows - I've read a few books and looking forward to the live TV event next week then today I read on another website a chap from the US who took his telescope out , got distracted and eventually got dew on the lens (not the mirrors I believe) which then left spots on it after it had dried out.

knowing how cold it was last night I'm guessing frost and dew are going to be a big problem here in the UK so am now wondering whether I had better get a dew shield before I venture out of the bedroom. The heated ones I saw are about £60 + a power pack which seem about as much again. Having already pretty much blown my initial budget could someone point me in the right direction as to how important the dew shield is and any suggestions for one would also be appreciated (and any more kit I need to invest in to get started)

Apologies for being so long winded - but enjoy reading the forum even before I step outside in the cold and so far mostly cloudy S Wales skies.

appreciate your thoughts - Steve

[sunshine185]

I wouldnt bother with a dew shield tbh,I have the same scope and although it does get a lot of dew on the outer tube, the mirrors don't seem to be affected. When bringing the scope back inside you can do one of two things that seem to be commonplace, either put the caps on before bringing it in, or bring it in and keep the tube horizontal with the caps off until the mirrors clear. You will get some super views with this scope, last night was the best view of the moon and Jupiter I have ever had.

[bish]

The time you realise you could do with a dew shield is the time you can't observe all night because it's all misted up. A dew shield and 12v hair dryer have been indespensible for me.

[sunshine185]

Forgot to add, dew shield are normally needed for maks and sct's, with a dob you could put a dew shield on the end but the primary mirror is still roughly for foot away from the shield.I came in last night and rested the scope horizontally,I looked at the primary and it looked horrendous, totally misted over with various lines and marks all over it, left it like that for half hour and it had totally cleared up, so I put the caps on, stood it back up and shoved it back under the stairs ready for tonight.

[assasincz]

Forgive my ignorance, but I do not see any reason to get a dew shield (or even heated one) for a newtonian reflector. The mirror itself is embedded deep inside the OTA and the tube itself functions as a dew shield. I have never had any problems in this regard.

Dew building up on the secondary mirror (which may be way more exposed) is, as I understand it, very rare (never happened to me) or occasionally happens with truss-tube OTAs. I reckon a dew shield (or a shroud cover for truss-tubes) might help here if that is the case.

As for the eyepieces, leave the cap on when you are not actually looking through it and avoid exhaling at it.

I would however suggest that you make your own dew shield for the finderscope (I made one from 0.5 litre bottle, fits nicely), that indeed is useful all year round. Or, come to think of it, you may just leave the cap on while not using the finder, problem solved)

There is, I hear, one advantage to using a dew shield on a newtonian - it helps to reduce stray light and supposedly enhances contrast, but I am given to understand that this is really of any use in cases where the focuser is at the very edge of the OTA and the light from the background, unobstructed by the OTA, gets into the focuser tube and into the eyepiece. A dew shield helps in this matter because it actually elongates the OTA.

The dewing issue, in my view, starts to be a real pain when you bring the scope back home and leave it in a warm room. The primary and secondary mirrors dew up, but there is such a small amount of mineral content in air moisture that it rarely leaves stains on their surfaces. Leave the OTA uncapped to let the moisture escape and make sure that there is no dust getting to the mirror while its left to dry (it may otherwise stick to the mirror) and I reckon you will be ok. A fan on the back of the primary mirror cell helps to speed this up.

That is all from my experience, but of course, I may be wrong in some remarks, so I suggest waiting for contributions from those more experienced ones.

[sunshine185]

Can see the advantage of sticking some sort of shield over the end of the tube, I heard some people use a kind of camping mat cut to size, however, as the op says, it would cost a small fortune for a heated shield plus a power pack to run it, IMO it would be a waste of money which could be used to buy some very nice accessories.

[John]

I use a flexible dew shield on the top end of my newtonian but its to shield light really - I've not found dew a problem either on the primary or secondary mirrors.

You might want to keep a few £'s in hand to upgrade / change the finder. The supplied optical one is decent quality but many folks find a reticule finder like a Telrad much easier to use.

[todd8137]

hi sounds like your good to go for next week ,some of my eps mist up alittle esp when ya nip in to make the last drink ect and come out to find that failing all that what i do is, (get a old cotton shirt cut a couple a 8 inch squares sow together) get my home made square of materiel place over ep and attach a elastic band,or just take the ep out and keep it in me pocket,

congrats on the new scope 200p are popular and will open your cosmic world up, get ready for many wow factor moments and a obsession with the weather,and get some good gloves and a good hat its gonna be freeze in cold next week

good luck

[stevetynant]

thanks folks plenty to think about there for sure

Would you believe it - in between me posting this comment and looking back at the replies Fed Ex have just delivered my new Dob to the door - but the wife has planned to take me to a family party tonight - oh well perhaps all day Saturday to get everything started and map out what I'm trying to find in the night sky - supposed to be a bright one tommorrow so fingers crossed.

By the way -the US guy who had spots all over his scope was at his cousins place just outside the Yosemite National park - thats an area of high volcanic / geyser like activity I believe so as has been mentioned perhaps his issue was one of mineral content in the mosture/atmosphere which is unlikely to be an issue on a mountain in S Wales I guess.

Planning my first night out away from the street lights where I live- Dob, EPs, small table, Coffee, plenty of warm clothes, Turn Left at Orion and Google skymap on the phone- anything else I'm likely to need?

John - thanks for the Telrad comment - not sure how much these are - will have to do a little research again I guess and break it quietly to SWMBO.

[sunshine185]

I only ever observe from my back yard and one thing I can definitely recommend is a garden chair, just got a cheapy white plastic one but is far better than crouching over the ep for hours on end.

[Rob L]

I agree with all the above, you don't need a dew shield. But you might decide you need one for the finderscope.

A Telrad or Quikfinder is a great investment and transforms star hopping. There's always something else to spend your money on in this hobby I'm afraid.

[bish]

I've had the secondary dew up. You can get the hair dryer on it, or stick a dew shield on to prevent it. The majority of the time I don't need it, but wouldn't be without one just incase.

[zero_circle]

Just came in from a good session. I think the sky has been the clearest since I got my scope - Pleiades and Orion were beautiful. Had to come indoors and sample my latest batch of beer that has just finished brewing (Hooray!) By the time I got outside again my poor Telrad and EP's had misted up. Is there anything I can do to prevent this or is it just a case of keeping a lens cleaning cloth to hand?

[John]

Telrads are rather prone to dewing - you can get / make a dew shield for them though.

Eyepieces are best kept at a bit above the outside temperature. I keep mine in a foam lined case which is shut in between getting an eyepiece out. The foam seems to retail a little heat for quite a while.

[zero_circle]

Excellent - Thanks for the tip. I have just been keeping the EP's in the accessory tray but I have a nice foam lined case arriving in a couple of days. Hopefully that should keep the dew off them!