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Yeah, wooden roll off seem less dew laden. I was an occasional user of one thats 10 years old and only now showing need of TLC. I only once encountered water on the scope optics when opening up.
As it happens, I ordered an additional dewheater which arrived yesterday. I will try mounting that down by the mirror cell of my Newtonian and leave it on when not observing. I shall see what happens.
I will also start assembling the RPi bits for a longer term project.
Thanks to everyone for their observations. An alternative view helps.
I think I have to separate the problem into two parts to make it easier to grasp.
During observing: I used to have an AE 10” with thick tube walls and insulating the tube walls certainly seemed to help. The OOUK 12” has much thinner walls on it and so less thermal inertia, so it may not solve the problem entirely but, with a 12” dewheater up by the secondary it may be enough to avoid the faint mistiness on the main mirror I see on some nights. I leave the mirror cell fan running always – drawing a small amount of air down the length of the tube.
During daytime: I’ve been parking the tube inclined upwards at 5 degrees to help the water run off the mirror. I also have both ends open but with a muslin cloth over the end near the eyepiece to catch any smuts from local garden bonfires (it has happened – one of my neighbours went through a pyromaniac phase).
Air is drawn down the tube and out past the main mirror using the small fan in the mirror cell. The rationale was that the mirror front surface would more closely follow the air temperature if the air was moving rather than stagnant. The hope was that any periods of dew would be minimised. That worked badly!
I usually leave a gold coloured accident victim type mylar blanket over the scope to avoid drips from the roof affecting the tube. I tried having a cat blanket underneath the mylar in case that helped, but it didn’t.
I suppose I could increase the fan power or even reverse it so the flow is fast near the mirror and improve heat transfer – but it is heat transfer to the rear of the mirror rather than front. I could put a heater directly behind the fan too… Or even a fan in the tube side (but its a feeble tube anyway and I would rather not weaken it).
Alternatively: I could nearly seal up the tube when not observing and use a Raspberry Pi to monitor the mirror and tube temps (air proxy) with IR sensors and, if need be turn on the heaters and fans accordingly.
An RPi and 12V fan doesn’t use much power and if it worked I could try one of the RPi Zeros instead. I doubt if the heater would be on for long – especially if the tube is insulated. The Rpi would generate a little of its own heat but I have no idea how they cope with sub zero temps.
Has anyone else tried anything like this. What do Planewave and Celestron do with their dew control approaches?
Looks like I need to revisit the power being used.
We had a couple of 2-3C daytime temps followed -4 to-5C nights and now, with a 12C warm, wet front suddenly going through, heres the result….
I’m worrying whether the Pulsar dome is just too damp for C14… The NEQ6 was streaming with water today. I am aware of at least one group I know trying to line a Pulsar dome to stop dripping.
For the record its a 300mm mirror in a 1200mm tube.
Attachments:
I made PV Cep 16.75 (Gaia g unfiltered) on the night of the 2nd.
Picture:https://britastro.org/observations/observation.php?id=20250105_000432_f426e583e7f058d1
I have not yet measured tonight’s images but the activity around the HH region is still going on – its a continuation of what Richard Sargent spotted in November.
Will probably process all my data tomorrow…
A miserable spring and dreadful Oct-Dec here in cloudy Wiltshire…
The number of clear all night instances has been very low.
As space is short in the page limited Handbook, could thought be given to removing pages 117 and 118? Surely its pretty much unchanging from year to year and readily Googled? I think I used the pendulum equation once as a teenager.
Similarly, as a space saving/creating measure, could the line spacing on page 116 be changed? That might free up ~1/3rd page that could be used for some small item like expected dates of observable Earth flyby/gravity assists.
I also wonder who looks at the Bright Stars info page. Genuine question: who uses it?
BTW none of this should be taken as criticism. A huge amount of work must go into creating the Handbook and I for one am very grateful to those who put in the hours. As a result of their work I’ve already started to plan my 2025 observing year. Its good to see the Handbook evolving. Thanks to all involved!
Every time I image an 18th magnitude star for variability or capture a 17th magnitude nebula, I wonder at how things have changed over the last 30 years.
I enjoyed visual observing before neck arthritis stopped play, but these days I get a kick out of what we can do via imaging.
I remember looking at long duration photography in the 80s and thinking I would be really smug if I reached 13th mag with my 8″ Fullerscopes Newtonian and some Tri-X. Its a 1sec exposure with a modern CCD.
You should be able to sync into the existing T-Point model, but given that when using the automated platesolving mode it takes less than an hour for a full T-Point run, I would be inclined to redo the T-Point from scratch. Just wait for a night with thin cloud or full Moon thats no good for anything else. I find 1-2second images are easily deep enough. I just listen to music on headphones while manually rotating the slit to ensure the scope sees skies – the joys of a non-automated early Pulsar.
IF with an accurate time and an accurate position you still have issues it will help focus your attention a bit.
Just bought a second hand MX, but have not yet installed. Hopefully a lot better pointing than the NEQ6.
Nor can I. Not sure where it went.
Bottom line: Google Earth is your best bet as TheSky doesn’t (I don’t think) talk to a GPS dongle, so any location it has for you will be from an IP address or the nearest town long/lat. I could be wrong here.
Note though, that time and location are both important. You need a good position and good times. So, to get accurate pointing:
1, Set the computer system clock using its “Change date and time” setting.
2, Start TheSkyX
3, Set your location to the Google Earth value
4, Do your 100+ pointings T-Point run.And whenever you use the telescope set the time again just before running TheSkyX – its an essential. Many laptops/PC lose multiple seconds over a week or two between observing sessions – some do better than others.
Not sure what mount you are using, but a Paramount MEII does far better at absolute pointing (after T-Point) than my regular NEQ6 which was good to 1 arc mins on the west sky last night but a lot further out on the east part of the sky. The mount quality is a big factor. If your mount is not entirely consistent even T-Point cannot make it perfect.
Ah, the code is 19 years old. Am impressed it ran. Do you know what version of Windows the previous owner was using?
It might be worth:
1, Try a newer serial port cable
2, If running on a modern version of Windows run TheSky6 in an appropriate compatibility mode ie if was running on W98 run the TheSky6 application in W98 compatibility mode on W8, W10 or W11
3, Get TheSky6 licence transferred to you, set up SB account and raise problem on their help groups.
4, Consider buying the previous owner’s laptop with working code on from them. 🙂
5, Consider updating to TheSkyX plus necessary add ons – expensive possibly.When you set up the mount, the weights should be adjusted so that if you disengage the gears/worms (only do this if someone has a very firm hold on the counterweight arm) the telescope can be pushed to any position by finger.
Is that the case with this mount? If the telescope is strongly out of balance then the Home request may fail.
Also, am not quite clear from what you wrote. Does it complete the Home operation (with two tone noises) and come to a complete halt without producing the error message or does it only produce the error message when you try a subsequent slew?
I am with Martin on this one, the help support from the SB website is a good place to look to cure this problem – but its not rapid.
Paul is more experienced, but the way I would start out is.
Install TheSkyX
Install the driver
Connect USB cable to mount
Set mount into balance position and reengage the gear.
Power up mount
Sync the laptop time in Windows
Run TheSkyX
Make sure your location is set (Google earth can give long/lat)
Tell TheSkyX to Connect to mount (I assume its an older mount and you select the COM port first – newer mounts don’t need that)
Tell TheSkyX to Home (listen for 2 tones as it slews in RA/Dec)
Choose a target not far from Home position using the cursor and slew to that… Watch the OTA to check it moves in both Dec and RA….If it does all that okay you’re 9/10ths there.
Personally I would ignore the hand controller until everything works fine from the computer as thats the best way to schedule a public viewing.
It may not end up pointing at the target you selected until the thing is polar aligned. Doing a brief manual TPoint was the way I worked out the adjustment initially using an OTA with a 1 degree FOV. TPoint provides instruction on whether the Azimuth or altitude needs adjustment – and how much.
Theres a list of error messages here: https://www.bisque.com/wp-content/cs-content/help/scripting/thesky6/software_bisque_error_codes.htm
I couldn’t find error 2003. Did you mean 22003?
