Last updated: 31 January 2003
Subject: ETX-105 Cold weather issue Sent: Tuesday, January 28, 2003 16:36:46 From: firstname.lastname@example.org (Simonich) Here is an Email discussion I had with Dr Clay. You may add it too your site if you wish. [read from the bottom] Dave ---------- Fantastic and thanks for the update! Clay ---------------------------------------- Dr. P. Clay Sherrod email@example.com Arkansas Sky Observatory MPC/cbat Obs. H43 / Conway MPC/cbat Obs. H41 / Petit Jean Mountain www.arksky.org ----- Original Message ----- To: Clay Sherrod Hi Dr Clay - Well I gave the scope the acid test tonight, or should I say freeze test. As soon as I got home tonight I moved the scope outside. 3 hours later I went to do some observing of Jupiter. The views were much much better, even at high power. Extreme cold does take the scope that much longer to cool down. Tonight it was 2 degrees F when I finally went out. I used the scope in purely manual mode, and while noticeably stiffer everything still worked smoothly. Actually the scope cooled down so much that when I brought it in after I froze up the condensation formed and immediately turned to frost. Thanks again for your advice, and I'll forward your advice to Mike to post on his site. Dave ----- Original Message ----- To: Clay Sherrod Thank you for your quick reply. I'll try to be more patient an let the scope cool down longer. Dave ----- Original Message ----- From: Clay Sherrod Hello Dave...with temperature extremes like you are experiencing I doubt that you are going to get good views at all for three reasons: 1) air unsteadiness, worse when the temperature is coldest; 2) tube currents; you must allow at least two hours for your scope to cool down to ambient temperature; 3) the 26mm eyepiece is horrible for sharp images; Meade used to provide good quality Plossls, but they are very poor now....the 26 is the worst and has much flaring around the edges. I think the cold sky conditions are your key here....NOT the telescope. When the seeing is that bad, just back off and enjoy deep sky low power objects like nebulae, clusters and galaxies....or some of the new comets! Clay ----- Original Message ----- To: firstname.lastname@example.org Dear Dr. Clay - Recently I have been noticing that on bright stars like Sirius, I am getting some flaring, and last night which was very clear and steady here I am barely able to see any detail on Jupiter, or the Cassini division on Saturn, even with my 26mm eyepiece. THe scope is a year old now and I know that I was getting crystal clear views of the planets when it was new. The strange part is that I seem to be seeing decient views of nebulaes like M42 & M43. Could it be because they a fuzzy by nature so I am not noticing the difference? The only other detail that may be worth mentioning is that it has been very could out this way lately. It was 8 degrees F out when I came in last night. I would appreciate and thoughts you may have on this. Thanks, Dave
Subject: Cold weather scope usage Sent: Thursday, January 30, 2003 5:02:24 From: AlanM@peoplepc.com (Alan McDonald) To: email@example.com I saw your thread on cold weather performance with Dr. Clay, and I thought I'd add a few thoughts for you to consider, since I live in Michigan and deal with cold weather a lot as well: 1) When plastic gets that cold, it gets really brittle. Be very careful with it because the plastic will have very little flexibility or impact strength. Be careful not to bump it or stress it, because things that are OK at room temperature can lead to cracks at very cold temperatures. 2) When the meniscus gets that cold, your breath will condense and freeze on the lens on contact. The eyepieces also can freeze up just from the vapor coming off your eye and face. Your session will be pretty much over at that point if you don't have a dew remover gun (you can switch eypieces when they freeze). A dew shield helps quite a bit too. 3) When done, I take my hard case outside and pack the scope (being careful not to breath on it so the icing stays to a minimum) and eyepieces in it, and close it all up before bringing it inside. I leave the case closed for at least 12 hours so that the scope can slowly warm up, and then take it out so that it can finish warming and drying. By doing this, I get none of the icing and condensation on the scope that you observed. I try to avoid the condensation, because I expect that the drips that form could enter the tube, thereby increasing the humidity in the tube during storage (and maybe fogging the primary mirror on the next cold observing session). As a general rule, I try to avoid observing sessions when it is much below 20 degrees F, as I think it is just too hard on the scope to keep sending it through those severe thermal swings - but I might just be overly cautious on that one. Alan
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