gerardsheldon

I am thinking about the getting a Televue 1.25 inch 3x Barlow and using it to image with a DSLR. According to the chart from Televue, Tele Vue Optics: Barlows the magnification is much more than 3x, and with a DSLR it would be closer to 5x (the DSLR image sensor would be at least 100mm from the surface of the barlow). As my telescope has a focal length of 650mm,(f5) the focal length with the 3x barlow would be about 3250mm (f25) for imaging. So, in other words ignore the 3x when considering imaging. 1) Is what I have written above correct? I ask as the TV chart shows the magnification for 10mm and no camera could get that close, and does not show the magnification greater than 100mm which can happen. Have I misinterpreted the table? 2) Do other companies show a table like this? Thanks

Thanks very much for all your replies. There are a number of options and I'll explore what works best. Gerard

Thanks Ed, where on the telescope did you attach the weights? Behind the mirror, or on the top, bottom or side of the tube?

I would appreciate advice on balancing my dobsonian about the atitude axis. I have a skyliner 250p dobsonian flex tube. When I release the altitude tension handles, the eyepiece end of the tube swings down towards the ground. It would be extremely difficult to move the centre of gravity to the correct position as it is a collapsible open tube assembly. The centre of gravity lies where the three struts in the middle between top and bottom tube segments. Please see picture at the following link: https://www.rothervalleyoptics.co.uk/skywatcher-skyliner-250px-flex-tube-dobsonian-telescope.html This is becoming more important as I want to build an equatorial platform. Has anyone got a good solution? Gerard

Thanks for the information. This all looks so much easier than what I have read elsewhere, so I want to give a go. I have not had a lot of experience with wood or metal. I would be grateful if you could help me with the following questions: 1. Does the size of the pillow bearings matter? I can't find 18mm. Could I go for 17mm? 2. Did you cut the steel shaft using a hacksaw? 3. Can you change the speed of the motor a lot? I have a concern that it will either go too fast or slowly and I won't be able to adjust the motor to the right speed. Any advice would be greatly appreciated. Gerard

Thanks. My mount is a HEQ5, so it does a good job when autoguiding. Using a barlow would mean the camera would be further away from the telescope which could cause balancing issues and shake possibly? don41 has got good results from using a focal extender - are there any issues I need to be aware of?

I have a 130 Skywatcher pds f/5 and use a modified DSLR 1000D. Lots of astronomical objects, like the ring nebula and many galaxies, are really small in the sky. when I take pictures of them, they occupy a very small area in the photograph. Magnifying them with a barlow (I have 2x televlue one) would also make them fainter and my tracking would have to be good. Does anyone have any advice about whether I should use a barlow or not?

Thanks for your posts. the model is a 8 Ah Li polymer tracer battery. Model is BP2544. I am bit confused as the HEQ operating voltage is between 11 volts and 15 volts and on that basis the Li polymer should be OK. The flashing lights is warning that the voltage is low but perhaps not too low. The light flashes more rapidly when the voltage drops further. However, there was one post above that says the HEQ5 is happier above 13volts. I'll probably just get another battery as I don't to take the risk of wasting my time. By the way, I find typing here very slow for some reason and the computer can freeze.

I tested the tracer polymer battery over a six hour period and although the red light on the HEQ5 flashed most of the time, and more rapidly as time went on, the mount moved so that the time on setting circles changed by six hours, suggesting the mount will track OK. (the test was carried out during the day). I did not try to get the telescope to point in a different direction using the handset. 1) Should I be bothered by the flashing lights on the HEQ5 mount? 2) Is tracer misleading people by saying their batteries are 12 volts? (they say that their discharge curves are flat) I found that the battery's voltage falls. Below is from the Tracer datasheet. ---------------------------------------------------------- Built-in Fuel Gauge - 5 colour LED fuel gauge mounted externally to show charge level. LED Status: 3 green & 2 red: Battery fully charged 11.7V 2 green & 2 red: Over 50% capacity 11.4V 1 green & 2 red: Over 20% capacity 11.1V 2 red: Less than 20% capacity 10.7V 1 red: Less than 10% capacity 10.3V No lights: Battery empty 8.25V ---------------------------------------------------- Thanks Gerard