Having never used one of these at all, I thought I'd get a few opinions.
Suppose you had a good view of the SCP, but were in the light-polluted suburbs most of the time. How would you rate using a polar alignment scope in say, an EQ5? Are they any good at all here?
I have seen listings for several types from different manufacturers, but not yet one for the Southern Hemisphere specifically for a SW EQ5, although I believe they exist.
I'm well aware of drift aligning too, and open to trying that as well, although I only do visual, and really don't care about a bit of drift.
The sum total is that I need a better method than at the present, which is simply using a good compass and a graduated bubble level. The Synscan is just too intolerant of sloppy setup.
Geoff, i have a pretty good view of the SCP but unfortunately its right over a main road so lot of light pollution in that direction. I have for some time pondered on the idea of using a Camera attached to one of these polar scopes. Recently I saw myastroshop have released something like this. Using the GSTAR-ex camera with a custom made polar scope mounting rig. You can find it a third of the way down on this page
I would prefer to use something like a Qhy5 or similar guide camera to do the same. The qhy5 mono i have is quiet sensitive, and I think would work. Just not sure how to adapt it to this. I know now there is a Video Finderscope you can get that uses the Qhy5 guider, so I think its possible to do. Just need to work out how you would adapt a Polar scope to this.
I have a HEQ5 Pro with the polar scope. I have not had a chance to use it in Sydney yet but I used it at Wiruna this month and after eventually identifying Sigma Octans and lining it up with the gratical marking I found it was quite accurate to do a goto with the synscan controller without any further alignment by starting from the home position and syncing the first alignment star.
The FOV of the polarscope is about 6 degrees. I set my mount to -33 00 00 (Wiruna House) with a protractor and spirit level and used a compass to find aproximate south. Sigma Octans was in the FOV but it took me a few minutes to identify it (I forgot the view would be inverted to the view I was looking at on Stellarium). It was then just a matter of adjusting the Azimuth, Altitude and rotating the RA axis until the graticle markings lined up with the stars. Only made difficult by my failing eyesight and bending down to get a look into the polarscope.
In the workshop I tried the Gstar mount with standard web cam, I could not justify the expense of the Gstar. I then made my own bracket (and sold the one from myastroshop). This arrangement was not sensitive enough barefoot but PHD recognises the web cams and when the exposure was increased to 2 secs the stars become visible. I have not tried this method on Sigma Octans yet because I have not had time, but expect it to work like the Gstar.
Barry
I actually only bought the HEQ5 Pro to experiment with and try the polarscope.
The first pic is my modified i8800 web camera
The second is the view on the PHD screen (2secs)
The third is the published picture of Sigma Octans from IIS using the Gstar.
Last edited by Barrykgerdes; 02-04-2012 at 09:07 AM.
In my opinion the polar scope is a gimmick if you try to use it anywhere other than in a REALLY dark site, if the mount is on the red light washes out any chance of seeing Octans' stars at all and you cant dim it or turn it off when the scope is on.
As Barry has posted, you can sort of see Sigma Octanis when the scope is in the right area and the mount is powered off but your eyes need to be completely dark adapted.
For the tutorial, I used my Binoculars mounted on a bino mount on the piggyback screw that is on one of the tube rings as the binos have a nice wide field and being 11 x 70's, plenty of aperture to see what is there.
I first made sure the scope and the binoculars were coaligned so the main scope (and therefore the polar scope) were pointing in the same place as the binos. At the time I did the tutorial, I was using the EQ2 with no polar scope, but I have reproduced this method with the HEQ5 and it is spot on. Once pointed, the RA axis is manually rotated (with no OTA or counter weights on it) and left powered off, to visually inspect it lines up. Then you can fine tune the mount if necessary.
This is what I did when I first aligned the HEQ5 and was able to take unguided shots up to 1 minute before very slight drift occurred.
Now, I simply use Trevor Gerdes guide to using PHD and the guidescope to drift align in about 3-5 mins.
For visual and I am assuming from the same place in the backyard, simply try my method (as Achenar is in the right spot at the moment based on my starting point in the sky). Once done and verified, mark the tripod leg positions on the ground with paint (for concrete) or pavers for grass and then plonk the scope down there each time and you should be right.
DONT rely on the altitude scale on the mount to be ANYWHERE NEAR correct.....both my EQ2 and HEQ5 where about 10 - 15 degrees out.
EQ6 (basic one) has very strange and not well designed LED circuit.
I had to replace 2 original resistors on the main PCB with much higher values to get reasonable behaviour of the circuit (that means. the intensity of LED is now appropriate for dark conditions, it is not blinding me any more and the intensity can be actually adjusted) .
I also replaced other resistors (in series with ON LED and the ones in remote control box) so now they are glowing with reasonable intensity in the dark (no, they are not visible during the day any more ).
The mod as I did it is here: http://www.iceinspace.com.au/forum/a...se.php?a=53912
Reference to the illumination. I have the 3.27 version of the synscan. Adjustment of the polar scope LED is via the set up menu, handset setting Polarscope LED using the L/R arrows. From the Wiruna dark site the optimum level was 8% (about the middle of the range for one bar showing on the hanset). This gave just enough illumination of the graticle to still see Sigma Octans.
The biggest trouble with the Sigma Octans asterism is seeing the 6.5 magnitude HIP 112355. This takes a dark site to recognise in the polar scope. Its limiting visual magnitude level can't be much better than about 7. The othe three stars at 5.5 magnitude are much easier
Barry
PS a note on the webcam: I use the webcam focused at infinity and afocal viewing of the polarscope
Last edited by Barrykgerdes; 02-04-2012 at 11:02 AM.
I had often noticed that I would get repeated fails on 3-star alignments, but be successful on 1-star (of course I would though) and 2-star efforts. What was it telling me? Getting closer to the answer.
I have decided that a polar scope is not on order for the time being. I think at this stage it is something about crafty usage of the Alt-Az fine adjustments on the EQ5, on a 1-star alignment, which is then repeated a few times in different directions. The results will send me a message. This is what you are really doing when setting the scope up with a compass etc.
I have a HEQ5 Pro with the polar scope. I have not had a chance to use it in Sydney yet but I used it at Wiruna this month and after eventually identifying Sigma Octans and lining it up with the gratical marking I found it was quite accurate to do a goto with the synscan controller without any further alignment by starting from the home position and syncing the first alignment star.
DONT rely on the altitude scale on the mount to be ANYWHERE NEAR correct.....both my EQ2 and HEQ5 where about 10 - 15 degrees out.
Good luck.
Cheers
Chris
Hi Chris,
Thanks for these details. Yes, I eventually woke up after some time that the scale just might be like a Govt Budget. Sure enough, it was 7 degrees out. Looks like that is one of the more accurate efforts from the rubber tripod factory
which apparently does the procedure I have been trying to perfect. Aha Essentially this involves doing a 2-star alignment, then slewing to a star near the meridian, and using the Alt-Az adjustments to centre it.
The Celestron All-Star feature is said to be the same.
which apparently does the procedure I have been trying to perfect. Aha Essentially this involves doing a 2-star alignment, then slewing to a star near the meridian, and using the Alt-Az adjustments to centre it.
The Celestron All-Star feature is said to be the same.
The Gstar Mount is just a bracket to fit the polar scope body with a slotted aluminium bar to hold the camera. It could be adapted to just about anything. I added an extra hole so I could turn the bar around to get more adjustment. I fitted three assorted web cams before I made a custom mount to suit a i8800 web cam mounted in a 2" x 2" x 1.5" aluminium box from jacar.
The aim of the bracket is to hold the camera in a position to image the polar scope eyepiece.
The FOV of the polarscope is about 6 degrees. Sigma Octans was in the FOV but it took me a few minutes to identify it (I forgot the view would be inverted to the view I was looking at on Stellarium). It was then just a matter of adjusting the Azimuth, Altitude and rotating the RA axis until the graticle markings lined up with the stars. Only made difficult by my failing eyesight and bending down to get a look into the polarscope.
Thanks mate, just the info I needed. I always wondered the FOV of the scope. This weekend im gonna finally try it out if I can.
Essentially this involves doing a 2-star alignment, then slewing to a star near the meridian, and using the Alt-Az adjustments to centre it.
