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Drift aligning

jambouk

By jambouk
in Discussions - Mounts

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jambouk

jambouk

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I had a go at this last night (without the aid of a computer) and the hardest part I found was making the corrections. Having said that I'm still not sure I know exactly what I'm doing and whether a diagonal means my corrections should be different and if so in what direction...

It was nearly impossible to make a small correction, it was either a massive one, or no correction at all, and it was as hard in azimuth as it was in elevation.

Are there any tips on how to make small smooth corrections?

Is it work lubricating where the mount head sits on the top of the tripod? It's a relatively new mount so no rust anywhere. AZEQ6.

Thanks.

James

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jambouk

jambouk

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Thanks both. It was the Ian King version I attempted to follow last night, but failed miserably. I was confused if having a mak-cassegrain or using a diagonal was reversing things as it just wouldn't work, plus my adjustments were like earth quakes! Also, when I went to try elevation, when the star drifted up, altering the elevation knob just made the star move left or right, not really up or down. This is an annoying hobby and not a good one when work starts early in the morning! :)

William, do I put some lithium grease over the paintwork where the mount head sits on top of the tripod?

James

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jambouk

jambouk

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Steve, that looks pretty straight forwards.

Do i turn tracking off when imm holding the W button for one minute? Also do the stars have to be on 0 declination exactly or can they be 10 degrees above or below that?

I will grease my mount and then give it a go.

James

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jambouk

jambouk

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I've just played with my knobs as i was putting my mount away, and they felt quite smooth. I think the load of the telescope and the counter weights makes it just much harder to make adjustments. I could use a lighter scope to do the drift aligning, but the whole set up must move when going from a scope which weights 5kg to one which weights 15kg say.

James

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Oddsocks

Oddsocks

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James,

Lithium grease can be used on the paintwork but depending on the type of solvent used in the grease it might soften or stain the paint, try a little soft furniture polish or beeswax, the solid sort in a tin rather than the aerosol type.

Lithium grease is ok for metal to metal surfaces.

When I drift align my HEQ5 and adjust the altitude bolt the star does move left and right at first because the mount flexes quite a bit before it moves up or down, I think this is quite a common thing and there are quite a few threads on SGL describing how users have to strip down and clean/re-grease the mount altitude axle supports on the standard HEQ5/HEQ6 to get a smooth motion for polar alignment even on brand new mounts but I've not read that much yet about the AZ EQ6.

William.

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jambouk

jambouk

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William, thanks again. Good idea about the furniture polish!

I will get some lithium grease and attempt to get it into as many places of the elevation mechanism as possible as i'd like it to be a bit smoother. I don't fancy stripping it down too much!

Thanks again for your help.

James

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DaveS

DaveS

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So how can you drift-align if you can't see east or west horizons?

My east is totally blocked by self-sown weed trees that the neighbour is too bone-idle to cut down and west is blocked to about 30 deg by houses, including mine.

Frustrated.

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MartinB

MartinB

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If you aren't sure which way make the adjustment, deliberately make your initial positioning of the scope so it is "out" e.g. azimuth obviously to the west and altitude obviously too high.  Then when it comes to making corrections you already know which way you will need to go.  Then take notes so that you will know what to do next time.  Print them on a sheet in big type and laminate!

Loosening the bolt that holds the mount to the tripod/pier will help greatly with azimuth adjustments.

Dave, zero dec at the southern meridian is well above the horizon.  You don't need to be too precise with this but the more you are away from the meridian/ celestial equator the more you will get drift in the axis you aren't adjusting.  Not the end of the world within reason.

James, if lubricating doesn't solve you issue of paradoxical movements of the star don't be over concerned.  What tends to happen is that the torque applied to the adustment bolts, esp altitude, causes this movement but tends to reset itself as the torque comes off so make sure you make enough of an adjustment to ensure the star moves in the correct direction.  Good balance of the scope is important to reduce these twisting forces.  

Keep at it and try practicing on nights when conditions are marginal then it isn't as frustrating.  With a bit of practice you will find yourself conquering the foibles and becoming quick and slick :grin:

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jambouk

jambouk

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Thanks. I like the look of that method of using a DSLR on the scope and reducing the angle. These are some questions I'#d private messaged to Steve (above), but which be useful if answered here for others who might also be unsure, with specific reference to the DSLR method:

- The author says to press West for one minute and then East for one minute at the slowest rate; for my skywatcher mount is that the rate 0 (0.5x) or rate 1 (1x)?

- Should I leave the mount tracking on sidereal rate when I do the procedure? Sounds daft, but is my finger on the handset replacing the tracking?

- How close to 0 degrees should the semi bright star be (+/- 10 degrees ok?) I thin Martin has answered this.

- When doing the elevation adjustments looking either East or West, do I still just use the East/West buttons on the handset as I did when looking south?

James

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  • 3 weeks later...
jambouk

jambouk

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Well I had a good go at the DSLR version tonight with my 180 Mak and AZEQ6.

In the day I'd greased up the elevation bolt and the mechanisms as much as I could. I still haven't got any wood polish but I'm looking for that to lubricate where the mount head sits on the top of the tripod to aid aximuth adjustments.

My polar alignment was pretty good to start with using the polarscope.

I looked east fist, found a lowish star, and tracked for 60 seconds in one direction and 60 in the other. The star had travelled quite far off the sensor, but it came back next to its starting point and I could see there was a gap, so turned the elevation bolt a bit and repeated; I'd turned the bolt the wrong way so did two mini turns the other way and repeated. It was spot on, so I then did a longer run, 2 minutes one way, then two minutes back; it was a bit off so turned the elevation bolt a small amount and repeated 4 minutes again and it was pretty much a straight line, so slew south.

I did a one minute one way and one minute back run and the line was straight, so did it again for 2 minutes out and 2 minutes back and it was still a straight line, so thought that would be good enough.

I'm managing to get 2 minute unguided subs with my 180mm ak, so I'm quite pleased. If it wasn't a school night I would have liked to have a go doing longer runs on the drift alignment process, it's just time consuming, but my handset is on a 10m lead so I can wonder around the garden.

So, so far, so good. I like the process. I suspect doing a few shorter runs to get it in the ball park makes sense, then do longer and longer ones to really test the polar alignment.

How important is it for this process to have the mount fully level? If it's not level, might problems in the alignment north/south or east/west interfer with the assessment of the other?

Thanks for the help.

James

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jambouk

jambouk

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I left it doing 2 minute subs of M57 for an hour; a few are a bit 'off' not sure if that is periodic error, or more likely the wind (natures, not mine).

I did a very rough and ready stack in DSS (with 5 darks also of 2 minutes each), and did very basic adjustments and came up with this..... (I'm going to ask a friend to give me a tutorial on processing DSLR images). I'm sure if I put my mind to it, I could get the subs up to 3 minutes :)

James

post-25543-0-13474800-1381356737_thumb.j

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Demonperformer

Demonperformer

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Oo and another question on a slightly different tack (without wishing to hijack the thread): does alignment correlate linearly with focal length?  Specifically, if I align my mount so I can get a 60 sec unguided sub with my 2m f/l scope, and have my camera with a 200mm lens piggybacking the scope, does this mean I will get 10 minute unguided subs, or would I be being overly optimistic?  Thanks.

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jambouk

jambouk

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Yes i got answers.

Leave tracking on sidereal rate all the time

I did my slew at rate 1 (on the rate 0-9 scale)

I'm not sure about the 0 declination, but i tried within 20 degrees of 0 (so zero +\- 10 degrees)

Use the east-west buttons always, whether looking due south, or to the east or west horizon.

I'm mot actually sure it matters if the point at which you switch from west to east appears on the cameras sensor, as it is just the distance from the start and finish point which needs to appear on the sensor (equally i don't think it makes a jot of difference if the sensor is oriented the right way and whether the line goes left and , up and down, just as long as you slew it west-east).

I posed the other question a day or two ago.

James

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