GeorgeCarey

Cloudy here... maybe tomorrow.

I heard about it last night but it was cloudy. No clear spells for a few days...

I would like to do some serious work, but I have no real idea how to start. I have some friends who do variable star work but that does not interest me much. I am interested in comets and asteroids, but do not know how to do scientific work.

Yes, I agree that for mobile use a finder may be necessary. However, when I have taken the scope off the mount for maintenance (cleaning the mirrors etc) and put it back, I have to find a star for the first sync. I do this in a few ways. 1 I hold a green laser pointer against the edge of the telescope mounting plate on the mount. 2 I sight along the line of the tube ring fasteners. 3 I sight along the edge of the telescope plate. 4 I look along the edge of the telescope and set it up so that a bright star can be seen near three sides of the tube. Any one of these is good enought to get the star on the camera CCD after one or two tries. I admit that it requires a certain skill to do this. Some of my friends at our astronomy club have tried it and failed. Others have learned to do it after a few tries.

Why do you need a guide scope? Once you have a good pointing model there is no need for a guide scope. Any object you want to aim at is very near the centre of the image. Rotating the OTA is not a good idea. The axis of the telescope will not be exactly parallel to the DEC axis. Your pointing model will be ruined if you rotate the telescope. George

Hi Lukas, I am the one who used a lead weight: I found a steel supplier who could make a steel strip of magnetic stainless steel (ordinary stainless steel is not magnetic). He curved the steel to fit the radius of the tube and I attached it to the tube with adhesive tape. I melted lead and cast a cylinder by pouring the lead into a mold. I bent the lead disc to the shape of my scope tube. I then drilled 8 small holes in the lead and glued small neodymium magnets into the holes. The magnets are very strong so I put a layer of felt over the disc. This allows the disc to be slid up and down the steel strip easily, and the magnets hold it firmly in place. I use the lead weight to give accurate balance in Declination, because a movement of the tube in the tube rings of a millimetre or two is too much. I also offset the steel strip because the camera filter wheel is off centre. George

That is good news! Will a representative from ASA be there? It would be nice to meet and speak to one of the team.

Perhaps there is an analogy with computers. You buy a new PC (ASA DDM mount). It comes equipped with Windows 7 (Autoslew). You buy Microsoft Office (Maxim). You buy Photoshop (Pinpoint).

There is a free platesolving program called 'Platesolve2'. I suggested to ASA that it would be a possible alternative to Pinpoint, but no interest was shown.

Last year there was a new astronomy show in the UK, the Midlands Astronomy Show. It was very successful and rivalled the long established 'AstroFest' in London. The show now looks like it will be a regular event: http://www.ukastroshow.com/ How about ASA setting up a stall at the show? There are very few DDM mounts in the UK, largely because ASA do not have a well known name here.

Glad to hear that you have the problem fixed. I am building a new scope and have bought the Telescope Express spider. The vanes look perfect but I will only know when I make the scope!

Hi Robert, I used the Autoslew comet tracking. It works very well!

To make locating objects such as comets easier I have written a spreadsheet that creates an Object List from an ephemeris. An account of this is here: http://geoastro.co.uk/objlist/objlistgen.htm I believe a new version of Sequence may make this redundant but until then I am using it. If anyone wants a copy please ask. George

I had a go at this early this morning. I only had about 20 minutes before the sky was too bright so I could only get 6x40 seconds in each colour.

Hi Ian. Are you going to use "Sequence" to make your pointing files? Because it was yet another level of software to struggle with I made pointing files the hard way by manually slewing to each star. After a couple of years I finally bought a full copy of "Pinpoint" and tried Sequence. I wish I had done so from the start! A 50 star pointing file takes forever one star at a time, but Sequence sails through the task. George

Are you choosing a star in Autoslew? I have never done this, as I only select stars in Cartes du Ciel, which is my planetarium software. Perhaps others do the same, hence we are unqualified to contribute.

Ddm60 or ddm85? Ah, just seen that it is in the DDM65 section.

I tried, but from my observatory there is a neighbour's tree in the way. I got this with a DSLR and telephoto lens from my loft window this morning. Rather poor, but at least I got it. The bright star to the right is Spica, and Mercury is near the horizon. I hope when (if) it has gone round the Sun it will be better placed.

As far as I am aware, Autoslew only uses two settings of motor parameters - tracking and slewing. The 'custom' setting is a speed you can use to fine tune the PID values, but I don't think that speed ever gets used. I am sure someone will correct me if I am wrong.

I assume you have got a good polar alignment? Before you make the new pointing file you could try deleting the old configuration. Then align on a star and sync. Then start the new pointing file. Ignore the message that comes up and says you need to sync - you already have. Do 5 stars in the West and 5 stars in the East. Calculate and save. George

1000 readings per second? I thought it was 100.

That sounds interesting! Before I volunteer to be a tester, can you let us know what the new Autoslew can do compared to the old? My Autoslew 5112 is working well, and does everything I need it to at the moment. George

Thanks, I see that you are in Australia. I wonder if such a fan would work in the British climate? I would be reluctant to cut a hole in my dome and find that it didnt work! I might try an experiment by making a replacement lower shutter and putting a fan in that. The lower shutter acts like a drawbridge and swings down and out when the dome is in use.

Does the fan draw air into or out of the observatory? Does it only run during the day? My observatory used to get bad condensation over the night, so in the morning everything would be wet. I installed a dehumidifier and sensor which keeps the RH below 65%. So far this has worked very well, but it does cost money for the electricity.

I found that I only got tube current effects when the telescope was at low altitude. If you do a test with the scope aiming almost straight up at the vertex it should rule out tube currents. George