Ppec?

[Hoges]

I'm wondering how much effect this would have for unguided exposures. I currently have an HEQ5 and guiding with an eyepiece is fine although a major pita. Unguided 30 second shots, maybe 1 in 4 (600mm/dslr) have tracked nicely. 1 minute shots, perhaps 1 in 5 are good. I'll check my drift alignment, but I would have assumed that if my alignment was off, then all the pics would be slightly out. If I can't do better than this, then it's time for a new mount and one with encoders and PPEC sounds like a good idea to me so I guess my question is, after some training runs to get PPEC working, how much difference would it make to an unguided photo? Could I reasonably expect to get 2 minute exposures with a 600 - 800mm scope?

The 'affordable to me' contenders seem to be the AZ EQ6/Orion Atlas version and the new AZ EQ5. Or would I be better off paying a little more for a Losmandy GM8? I guess autoguiding is on the cards but if I can keep things really simple and avoid it, I would.

Thanks - J.

[Slawomir]

Hi John

HEQ5 is a fine mount - I successfully used if for photography (up to 1200mm) for over two years.
Honestly, it would be much cheaper to get a guide camera and a guide scope than buying a high end mount with encoders for unguided photography. I do not think you could do unguided photography with either AZEQ5 or AZEQ6 at 600mm, you would still be throwing away lots of subs.

There is currently SBIG SG4 for sale on this site - it is a self contained guider so you would not need a computer in the field.

Just my two cents.

[NorthernLight]

Hi John,

I agree with Slawomir. After trying a bit a around with my EQ6 and finding that everything beyond 2min on 600mm was unuseful material, I went ahead and bought a guider (SSAG). It opened up 6min exposures on my mobile setup with nice round stars.
PS: when I set up I use a builders spirit level for the tripod and then the polfinder scope to pol-align. PhD does some DEC guiding but I haven`t noticed any issues with stars being not round at both 600mm and 750mm.

Cheers,

[Hoges]

Thanks for the info, guys. Looks like it's back to plan A! which was either put the synscan upgrade into the HEQ5, or sell it as is and put the money towards something with an autoguiding port - the AZEQ5 looks interesting.

I'll check out the SG4 - thanks.

[Amaranthus]

You don't need a ST-4 autoguide port with the HEQ5 - get an EQDIR cable and connect this to EQMOD with pulse guiding.

[Hoges]

Cheers, I'll check that out.

Spent last night out under the lunar eclipse and spent the first hour glued to the 9mm illuminated reticle eyepiece (200X). The star would start off in the center box and then in the course of a couple minutes would wander outside the box over to the edge of the first circle and then slowly meander back. Does this sound par for the course of a sub $2K mount? I should have lined up Jupiter in the eyepiece to give me an idea of scale - I'll do that next opportunity so I can figure out exactly how much PE there is. Looking at my first and last frame of a series spanning 40 minutes, there's a little over 1 arc min difference.

[Slawomir]

Hi John,

One arc-minute (60 arc seconds ) of periodic error seems a bit high...

Unless I read the info from PECPrep incorrectly, after adjusting worm engagement and installing belts I was getting around 15 arc seconds (+-7) of periodic error with HEQ5. This is the relevant graph for over 50minutes of unguided drifting: http://www.iceinspace.com.au/forum/attachment_browse.php?a=170518

[Hoges]

I'll pop Jupiter in the cross hairs at 200X and it will give me some idea of scale and how far the star is actually moving across the reticle - but it does seem a l o n g way!. Tried it with the mount balanced, east heavy and west heavy - not much difference. Hesitant to spend any time and money modifying mount if the worm drive just isn't that good. although rather weirdly, I took a 4 1/2 minute unguided exposure of M83 just for a laugh at the end of the night and while it's not sharp, it's only a tiny bit worse than any of my 30second exposures...(I've cropped it a bit - 80mm ED)

[Slawomir]

Not a bad shot at all John! :thumbsup:

It looks to me that you could improve camera's orthogonality to the optical axis; camera's tilt is particularly noticable in the top-left corner.

As for worm adjustement, it may or may not help, nevertheless, if you feel confident enough, here is a nice guide on how to do it: http://www.astro-baby.com/heq5-rebuild/heq5-we1.htm

[Geoff45]

From my personal experience of one G8 I would not recommend this route. Overpriced and substandard performance IMO. Had to get an SX AO unit to get acceptable guiding with a G8 and a 4" refractor.
Geoff

[raymo]

Hi John, The two HEQ5s I have used, would, if well P.A.d, give round
stars at between 120 and 150 secs depending on the dec of the target, at 1000mm focal length. Your 600mm should give around 200 to 240 secs, so your M83 shortened from 270 secs to around 220-240 would
probably have had round stars. It seems that the M83 represents your
mount doing it's thing properly. If only 1 in 4 30sec and 1 in 5 60 sec
subs are good, then something is seriously amiss. It suggests to me that there is play somewhere in the train, and once that play is overcome the mount tracks as it should, which accounts for the fact that the initially
elongated stars don't elongate any further as the exposure wears on.
If the tracking is so bad that 30sec subs are mostly no good, a 270 sec
sub would be horrendous.
raymo

[Hoges]

Thanks for the info, Geoff.



I wish!! Looks like I should strip it down a little and check/adjust where I can before I splash out on a new one. The other thing I don't like about the HEQ5 is that it's pretty jerky in it's movements when manually guiding - I often overshoot and it's 'oh sh$t, too far..press...press...press...that's better'



Cheers, It sounds like I need to do this.

[Hoges]

Sure was. I could put my finger on the brass gear that engages the worm and wiggle it 1mm or so either side. I tightened the worm set screws as per the instructions and when I put it back together there was no play at all that I could find. Hopefully, that will improve things, if not, I'll strip it and clean it all and try again. Thanks for the advice guys.

[Slawomir]

Great! Looking forward to seeing your new Astro photos.