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Seraph_69

First Light Tonight!! - Need Help!

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Hi all,

Going for first light tonight (finally) with my brand spanking Altair astro 8" f5.

Looking like clear skies all night but I have no dew shield or heaters, so I want to know what I should do about trying to avoid it as much as possible tonight.

Its just getting dark as I write this, so should I put everything outside now? Covers on or off and on or off or what?

How about when I come in later? Should I leave covers off things in the house then wait half an hour before capping the scope and eyepieces off again?

I have a tube cooling fan BTW but won't be observing until after my dinner so will it even need to be used?

Any other precautions I should be taking?

I have no power to my heq5 pro so will just be guiding by hand (I know, I know lol)

I saw the great Andromeda Galaxy through my finder scope last night and was amazed at that, so just want to get out there and see SOMETHING tonight, even if my setup isn't exactly adequate yet.

Thanks

Steve

Sent from my A0001 using Tapatalk

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Enjoy the evening, yes keep covers on until you are ready to start observing. When you have everything back inside, take the covers / caps off and as you have mentioned, leave for half an hour or so. Best that the environment you have the scope and eyepieces in is a slightly cool climate, away from hot radiators. 

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I wish you all the best I Didn,t have a dew shield when I started made one up from a camping mat,never bothered with a heater.When I,m done I leave the scope on the floor in the house until there is no sign of moisture put caps on and pack away.Having a good time is the most important thing above all else.I,d of got mine out tonight but there is scaffolding all around the flat

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Thanks guys, I got a bit impatient and ended up going out and just trying my luck. Was out for a good few hours, but just trying to figure out my equipment and just see something. Managed to observe the moon and had a peek at the great Andromeda Galaxy :)

I actually ended up capping off the scope inside and going straight to bed as it was late and I had work in the morning. However I left the scope in the extension, which stays pretty cold during the night (and during the day when not sunny today), plus blocked in by houses and a huge tree where I am atm, so didn't notice much of a dew issue last night. Only one side of the scope seemed to 'dew up', and didn't really affect my observing at all.

I do have some other questions regarding my observing though:

I have a 20mm plossl which came with my scope, and a 9mm plossl which I bought second hand. Everything seemed fine through my 20mm, but when I went to look at the moon through my 9mm, nothing but an out of focus blob? I tried racking the focuser all the way in and out to no avail. Then I tried with my 35mm extension tube to see if it was a back-focus issue? No joy there either.

I found I could focus on Andromeda galaxy with the 9mm but why not the moon?

Had the same trouble with my Altair 2x ED Glass Barlow lens and either eyepiece I believe. Think I tried both of the eyepieces with the Barlow, and with and without the extension tube (to cover all possible variables) and I just couldn't get the moon in focus : was really looking forward to seeing it's surface detail in close-up too :(

Any suggestions?

Thanks

Sent from my A0001 using Tapatalk

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You could try not putting the ep fully into the focuser I had the same problem with my BST and that cured it.

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So effectively creating a mini extension tube in a sense? Just not as long as 35mm?

OK I will try that next night I manage to get out there.

I also found that for some reason, the 9mm was a very tight fit in the focuser, compared to the 20mm? Surely 1, 1/4" is 1, 1/4”! lol

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It is just possible your 9mm eyepiece may be a Russian origin 32mm dia not a true 1 1/4".

A Barlow lens will move the focus point a good bit further out of the focuser, so you would need to bring the draw tube much further out to find focus.

Seeing and air turbulance can often make focussing tricky at times, especially at higher magnifications, even with the high quality eyepieces.

Keep practicing and it will all come together in time.

Good luck and clear skies.

Sandy. :grin:

Edited by Lonestar70

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A hairdryer is handy if you do dew up, a quick blast and the dew is gone :)

Just be sure to avoid getting the hair dryer / power cables wet.

/Dan

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Sounds like a cracking scope. 

Something to understand about dew shields and why dew forms - the primary goal of a dew shield is to keep some warm(ish) air in the scope tube (or at the end of the scope in the case of SCT / refractors), as dew forms when the air temperature reaches a critical point (the dew point).  By keeping the air temperature only a fraction above that dew point, dew can be prevented from forming.  Now, when you point your scope upwards some of the warmer air will escape from your tube or dew shield, the more vertical your scope is pointing then the faster the air will escape, and the temperature will drop towards the dew point.  Some nights the dew point will not be a factor because the ambient air temperature is not low enough, other nights there may be a lot of moisture hanging in the air so the dew point could easily be reached as the outside temperature drops (just check a car windscreen or similar for signs of dew).  A dew heater can help to maintain some air temperature around the end of the telescope tube but probably not indefinitely.  The air temperature in the dew shield could be 2 degrees C, if the dew point is 1 degrees then dew should not form.  You will likely see dew forming on the outside of the dew shield and on the cold metal surfaces of the scope.

You could keep eyepieces in your pocket (with the caps on) until needed, replace the cap when not looking through it to keep dew away from the glass.  I have tried dew heater tapes on the finder and eyepiece with indeterminate success, ultimately in my experience a dew shield does a lot more than a dew heater can alone, I think on many occasions a heater is not necessary.

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Thanks all for your comments, Lonestar - it is branded revelation astro, which I believe makes it a GSO eyepiece and would therefore have been manufactured in Taiwan.

Johnathan - this is very helpful. I am going to purchase a black foam roll matt thingy like what you would take camping to put under a sleeping bag, cut it to size and stick using a hot glue gun. Will maybe look in to dew heater mod for the secondary on the future, but if it ain't broke I won't try to fix it!

This leads me on to another question; I have a cooler fan at the back of my scope to help get it down in temp and avoid tube currents, I would obviously have it on at first to acclimatise the tube to the outside air temp. But how will this affect it with regards to Dewing? Should I be keeping a close eye on the primary and shutting off the fan asap once tube currents have gone to avoid dew? Or should this not have an effect?

Sent from my A0001 using Tapatalk

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Normally the air temperature is above dew point (otherwise it gets foggy and you may as well pack up anyway) so blowing ambient air onto the scope shouldn't cause it to dew up.

The scope drops below ambient due to radiated heat, this is when dew will form.

/Dan

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