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RobAro

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Posts posted by RobAro

  1. I had a very quick test of mine last night from my urban, light-polluted back garden.

    I mounted a Canon 50D (with extra battery grip) and a Samyang 14mm f2.8 lens (also a first light for this lens). I bodged a counterweight using a long 8mm bolt and a counterweight off another portable rig. The whole ensemble was mounted on a fairly wobbly Manfrotto 190 aluminium tripod. A cheap eBay intervalometer was used to set 30 x 1 minute exposures. Polar alignment was fairly rough and ready, just using a phone app to get the approx. Polaris position. To be fair, a 14mm lens is never going to stress the PA!

    First thoughts:

    1. You are never, ever going to PA this thing and then mount the camera afterwards. There's just too much movement in the tripod for that.
    2. The clip on polarscope light is rubbish. I need to come up with a way to attach it when the L-bracket camera head is mounted. There's a decent sized slot in the bracket to give an unobstructed view if you use a counterweight  to slide the bracket out of the way. I',m sure niothing nire than a bit of velcro will sort this bit out.
    3. I have no idea of how to set the polar alignment using the date circles. The manual is, at least, confusing. Being used to robotic mounts, having to start polar aligning by scrabbling around on the ground, peering through a poxy polarscope made me feel like a blooming caveman. Give me technology anyday!
    4. Using the locking clutch will almost certainly move the PA.
    5. A half decent tripod is a must for this thing. I've ordered a Velbon DV-7000 to see if that's a bit sturdier and will report back on this when it arrives. The DV-7000 is supposed to be a fairly sturdy little tripod of under £90.

    The results aren't going to win any prizes. This is the stacked image straight out of DSS with no post processing. The camera was pointed in the general direction Cygnus, though I paid no real attention to where it finally ended up. All the subs were fine, so the little mount had no problem here.

    The Samyang lens looks pretty good, with half decent star shapes (the focus could be better, mind). There seems to be a pretty severe off-centre vignette. Some flats would sort that though.

    Next steps:

    1. Test a better tripod.
    2. Test it with my 70/200mm f4 lens. This will give a much better idea of what the mount is capable of.
    3. Make a right angled viewer for the polarscope. I have a couple of RA viewers for camera viewfinders kicking around. I might be able to bodge one of them on.
    4. I wonder if I can extract the polarscope and replace it? I have a pretty expensive (for what it is) Losmandy polarscope, which has a superb polar alignment method. It'd be great if that could fit into the mount.
    5. I have no idea how to process extreme wide-fields in PS. I had better do some reading!

    14831420034_c289fe59d5_b.jpg

    Star Adventurer

    Hi,

    Just wondering if you had done any more testing with the DV-7000?

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