NGC 6888 / Crescent Nebula

[rjbokleman]

I've pretty much abandoned Polar Scopes or doing any kind of Drift Alignment these days. Instead for $299.00 and often for $269.00 you can pick up a QHY Polemaster that make this nearly foolproof. http://qhyccd.com/PoleMaster.html#PoleMaster

I own two of them. One for the AVX and one for the iEQ45 Pro. Frank, I mention this because Chuck also purchased one after I mentioned it to him. Ask him how he likes it.

[Chuck]

@ Frank and Ron:

When I started getting back into this hobby, about a year and half ago, I had forgot how time consuming it can be. Not only that, but a lot of patience for the right conditions also. I just keep plugging along, a little at a time, knowing things will come together at some point.

As Ron mentioned, I did purchase the QHY Polemaster a few months ago, after some email exchanges on equipment suggestions I was asking him about. It was very easy to install and use. The camera is very sensitive and I found you need to wait until well after twilight before using it. Doing the polar alignment is very quick but I haven't had a chance to try longer exposure imaging with my AVX yet. Ron has been using it successfully so I'm hoping it should be fine with my rig also.

Hopefully, the weather will start turning around soon and I can get back out there,

---- Chuck

[rjbokleman]

I've been very happy with mine and resulting Polar alignment has been spot on. Better even than I could do with a PHD2 Drift Alignment. I think the results in PHD2 speak for themselves. This graph is from the C8 EdgeHD /w OAG and .7x FR @ 1422mm.

[AndyG]

I've been very happy with mine and resulting Polar alignment has been spot on. Better even than I could do with a PHD2 Drift Alignment. I think the results in PHD2 speak for themselves.

That is indeed excellent guiding, but I would not necessarily agree that it is showing spot-on alignment, or better than what could be done with a drift alignment. The repeated southward corrections (red bars) counteracting the northward declination drift (red line) indicates a slight mis-alignment. Not that that is a bad thing, just not what you would see if the alignment were more precise.

Here is another example from last night (my gear polar aligned with PHD2 drift alignment.) Note the lack of declination corrections (no red bars):



As a practical matter, a small polar mis-alignment can actually be beneficial to guiding since the Dec corrections all go in one direction and guiding does not have to overcome the mount's declination backlash. The alignment just needs to be close enough to avoid field rotation (Field rotation calculator.) Any technique--pole-master or PHD2 drift--that can get you close to polar aligned is going to be good enough.

[NGC7000]

Beautiful image, Ron, and glad the PHD graphs were posted, too. I'm enjoying the discussion.

Tom

[rjbokleman]

Andy,

Slight mis-alignment and by slight we're probably talking about putting less than a gram of pressure on one bolt (Alt/Az) here or there.

That's one of the tougher things to realize early on is that using a PM or PHD2 you only have to apply gentle pressure on one bolt or the other to finalize. One mistake I made early is thinking I had to loosen one side or the other first then move the opposite. Nope. Usually there's enough play in these lower end mounts that simply nudging the tightness of one bolt will be enough to get you on target. In an AP mount I would suspect that there is much less 'play' to worry about.

It's also totally probable that since the mount had been sitting in this location since April and the graph shown was in July that it was off a bit. Shame on me since I never really checked the PA again given the decent guiding.

Things like wind, rain and dust / dirt under or around the tripod legs are enough to throw it off by a tiny amount. I'm also guilty of using a leaf blower around the patio to clear it off...probably adding to the issue. Additionally human error plays into this when taking the Telegizmos 365 cover on and off...I could have bumped it a bit too. You try to be gentle, but it's easy to bump things out of alignment when you're talking less than 1'. I suspect that was the case here. Was it enough to bother with? Not really at the time.

BTW, how do you manage PA remotely from here? Is there some motor driven capability in these AP mounts or did you set it when you left and hope for the best going forward?

P.S. This was the iEQ45 Pro, not the AVX.