Lidl "Computer Telescope" forum

Major problem!!
Last night I placed the threaded dew cap onto my etx and now it wont come off, its on too tight! I'm afraid to force it too much incase I do any damage, and with the scope this way it wont fit into the caryy bag. :oops:
Any suggestions for getting it back off?

if you grip it at the open end the dew cap seems to be much tighter than it
really is (it must distort slightly as you squeeze) try gripping it at the base
with the other hand gripping the head of the scope,
i found it easier with the scope pointing up
it should not require much effort to unscrew (im being very ginger with it as
i only got it last night, bloody clouds #@%£$)

wormhole

Marko

Major problem!!
Last night I placed the threaded dew cap onto my etx and now it wont come off, its on too tight! I'm afraid to force it too much incase I do any damage, and with the scope this way it wont fit into the caryy bag.
Any suggestions for getting it back off?

If you've had no luck so far, I might suggest using a flannel soaked in very hot water and, after wringing out the excess (wear gloves), wrap it around the tube end for a minute or so.

Now before anyone lambasts me, yes, I know the tube is plastic, but a tiny bit of expansion might help. I don't think the expansion would be enough to screw around with the internal optics. But I won't accept any liability :!:

Another solution maybe the use of a drop (literally) of either 3-in-one oil or WD40 around the thread of the dew shield. I'd recommend covering over the scope and the inside of the dew shield - DO NOT get any oil on the optics.

I would only suggest these measures as a last resort - the second-to-last potential solution. The last solution being a junior hacksaw :shock:

Dave

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if I had the telescope in equatorial mode I'd get piggyback exposures as long as I wanted - say 10 minutes, 20 minutes, half hour??

Theoretically yes, but you need to be very accurately set up for such long exposures and thats not even the worst problem.

Light pollution and skyglow!, if you take a long enough exposure youll see an orange fog appear on the film, obviously this depends on where you are and in a city or if there is abig moon out its obviously going to be bad.
You'll really have to experimant and see what works best for your setup, try using atleast so 400 film anmd start off by taking say a number of pics each say one minute longer then the previous, record what you do and compare it to what comes out, so you'll know better the second time around!.

As for in altaz mode (non-polar), you really are talking 20sec to 2 mins max!

Anthony,
I am going by shear memory but I recall something like 52 seconds for 60-deg altitude without any star trails being visible on film ... and something like 20 seconds near the horizon.

That's pretty damn short. I was hoping for a bit longer. That's the same length of time for exposing just on a normal tripod without piggybacking. Presumably if I had the telescope in equatorial mode I'd get piggyback exposures as long as I wanted - say 10 minutes, 20 minutes, half hour??

Anthony,

I think I owe you an apology as I may have misread your original query. If your mount is tracking and well polar-aligned, the figures I gave you are way off base for the simple reason they do indeed represent maxima for a tripod and non-tracking mount.

However, if you do have some sort of tracking and are polar aligned, these maxima will certainly increase. The extent of this increase will depend on how well you polar align the scope originally and also how well your mount tracks and further complicated by the field of view being imaged. For the latter, the wider the FOV, the easier it is to hide "small" errors and, to this end, the greater the possible exposure time. Ditto for altitude, for the higher the altitude, the less the relative (real) motion of the stars and, hence, the greater possible exposure.

Now, if you really want to "cheat" and shoot widefield and overhead, you will be able to get away with a fairly lengthy exposure even if the guiding is not perfect. I would not be surprised if a 120-sec exposure was clean in this regard.

Anthony.

Light pollution and skyglow!, if you take a long enough exposure youll see an orange fog appear on the film, obviously this depends on where you are and in a city or if there is abig moon out its obviously going to be bad.

Though if you do take images that are affected by light pollution please mail them to me. I can allways do with light pollution images!

www.irishastronomy.org/ilpac

Cheers,
~Al

Hi ETXrs,
I went out to the back garden with the scope and could see the moon through the high haze cloud, this time I brought out the camera to see what I could get.
Heres a pic of the moon (a rather poor one) using the Canon 300D and the 3X barlow, the exposure was too low, but I was deceived by the fact that it looked fine on the camera screen and when I put it on the PC it was faint.
I had to (but didnt want to) use the barlow as I was using the slot for the eyepiece for the camera and there wasnt enough focus run to focus the camera without it. Haveing such a bright object filling alot of the fierld of view is a bad idea as any defects will show much more readily.

The exposure was 600/sec at iso1600, I believe I can get better pics then this through this scope, note the dim yellow ring around the moon.
the high altitude hazy cloud blurred the image somewhat.
I haven't modified this image except for the brightness.
I've ordered the cable focuser as its nearly imposible to focus the image when the scope is pointing up high. I reckon this image is not focused fully.


www.irishastronomy.org/user_resources/fi...6-IMG_0648_small.jpg
BTW, turn your monitor brightness and contrast up full to see this correctly.

Just for comparison, heres a pic through a 100mm refractor and the same camera with no haze/cloud in the sky

homepage.eircom.net/~sac/graphics/moon/moon040403.jpg
I'm hoping that the sky will be clear tomorrow for another attempt, I always find that the images get better with experiance as no 2 scopes are the same, each having different quirks.


BTW, I may have jumped to gun in a earlier post about puting the camera on without counter weights, the scope is front heavy and when you place the camera on the back, it goes along way in actually balancing it !!