On Wednesday this week I was anticipating that it might be clear in the evening and I thought it would be a good opportunity to try and set up my 140mm Maksutov Cassegrain correctly on my HEQ-5 mount. I now have three stone blocks set up in the garden to rest the feet of my tripod on. Recently, I have been having trouble with polar aligning the scope and so, idly searching the net for help, I came across this video which gave me some ideas about how I could do things better.
I will describe what I did so that it may be of use to others. Firstly, I placed the tripod on the stone blocks in roughly the right position for true north. Although the three blocks are roughly levelled between themselves I adjusted the tripod legs so that top of it, using a spirit level, was properly level. I marked the location of the legs on the stone blocks so that I could replace the tripod in exactly the same place on another night.
Next I attached the HEQ-5 head and then made sure the azimuth adjustment screws were screwed in equally on both sides, so that the head was centred. I added the counterweight, then the telescope, DSLR camera and red dot pointer. I had been using a 50mm finder with crosshairs but I found it too heavy and it was awkwardly messing up the balance of the scope. The red dot pointer is much lighter and smaller. I then balanced the telescope in RA and Dec by adjusting the position of the telescope in the dovetail slot and by moving the counterweight.
I then waited until the stars were visible, lined up on Arcturus and made sure that the red dot pointer and telescope were aligned. I did need to take the camera off briefly to do this and replace it with a star diagonal and eyepiece but once the camera was back on I could focus the camera by using liveview and seeing the star on the screen.
Now, something perhaps I have not been careful about before was putting the telescope in the 'park' position before switching on the drive. This means that the counterweight is at its lowest position and the scope is pointing roughly in the direction of the pole. This helps when carrying out the alignment. Next came entering the usual date, time and location information on the handset (sometimes I get the date format wrong which can lead to all sorts of trouble!). When this is done the handset shows the location of polaris in the polar finder. This is in the format of HH:MM. From what I understand this is a 12 hour pointing system with 12 pointing directly up, 6 pointing directly down and the other locations increasing clockwise as on a face of a clock).
If you look through the polar finder you will see a small circle marked where you have to place polaris (northern hemisphere only). Suppose the handset said a time of 03:00, then you would rotate the polar scope until that circle is at the 3 o'clock position. Now using the azimuth and altitude adjustments on the HEQ-5 head only, move the head until polaris is seen in that small circle. Don't move the feet of the tripod as you might mess up the levelling you did earlier.
You should be roughly polar aligned. Then carry out a 3 star alignment. Not a 1 star or 2 star but a 3 star. This is something else I have learned. Do a 3 star as it is much more likely that the telescope will more reliably point to an object. Another thing I have learned is that you can do this ok with the camera in position. Just use liveview to centre the stars each time. Then you can be sure that the telescope remains well balanced.
I found that carrying this all out was entirely sufficient for my needs. Each time I used the controller to send the telescope to a new object it was reliably in the centre of the field. The video goes on to show how you can improve the polar alignment using certain functions on the controller which I might try sometime.
Finally, when dismounting the telescope I made a note of where the telescope was in the dovetail connection and where the counterweight was on its arm. When releasing the head from the tripod I undid the azimuth screws equally by one full turn each. Also I left the adjusted feet of the tripod as they were. Hopefully, this means that on another night when I go to set up I can return the telescope to exactly the same place and level and have the axis of the mount pointing in the same direction. It should speed up the whole set up process.
All text and images © Duncan Hale-Sutton 2024
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