Equatorial mount is sad

fivemack · 2017-03-22, 10:30

First half-decent night for months last night; set up the tripod and the EQ5 mount, put a camera with medium-sized lens on it, turned it on ... and the declination motor made a horrible crunching noise and stopped moving.

Managed one usable image (with a 50mm lens, Arcturus across to Denebola catching the Coma star cluster nicely and with a couple of perceptibly non-stellar fuzzy blobs where M3 and M53 should be), using my little portable star-tracker. Then the camera and the astronomer ran out of batteries roughly simultaneously, so I left one recharging with electricity and went in to recharge the other with hot chocolate.

What are peoples' favourite first-half-of-a-Spring-night objects? There are the two galaxy triplets in Leo, the globular clusters are starting to come out again (though it'll be midnight before M13 is in a good position); Jupiter is up but I'll need more focal length for him.

I think I need a darker sky before trying to do family shots of the Virgo cluster, though the 200/2.8 lens has a wide enough field of view to get some quite good compositions, and probably enough light grasp to get reasonable fuzzy blobs if I can figure out the tools enough to stack sixty twenty-second frames automatically.

xilman · 2017-03-22, 17:17

Quote:

Originally Posted by fivemack

What are peoples' favourite first-half-of-a-Spring-night objects?

Praesepe. ι Cnc is nice visually but I don't know what it will look like in your gear.

UMa and CVn are getting higher again. Check out sundry doubles and deep sky objects. M51, M81 & M82 are the obvious ones, but there are a good number of lesser known ones, some surprisingly bright. α CVn is an easy double and Y CVn an easy variable to observe and very red. The Wikipedia pages for each constellation should give you plenty of ideas.

Check out the current asteroid predictions and if you should be lucky enough to get several exposures you should be able to see the orbital movement.

R Leo is an easy VS but its period is so long you are unlikely to see variability. From the AAVSO: "R Leo, as well as any Mira variable, should be observed once a week".

Quote:

Originally Posted by fivemack

I think I need a darker sky before trying to do family shots of the Virgo cluster, though the 200/2.8 lens has a wide enough field of view to get some quite good compositions, and probably enough light grasp to get reasonable fuzzy blobs if I can figure out the tools enough to stack sixty twenty-second frames automatically.

A combination of astrometry.net and swarp is what I've been using on the Pleiades images you provided.

Swarp will also stitch together only slightly overlapping (or even non-overlapping) images if you feel like taking a mosaic of images.

Incidentally I've just started to investigate accurate photometry of your M45 image set to upgrade my skills and tools. I've a hankering to return to VS observing with a possible sideline in asteroidal rotation light curves.

I forgot γ Leo. Very bright Algol-class eclipsing variable.

fivemack · 2017-03-22, 18:11

It looks as if a correctly-pointed image with 200mm focal length would get me Amphitrite, Psyche and the M95/96/105 triple all in the same field of view. I think that's worth trying.

(http://www.heavens-above.com/Asteroi...&alt=21&tz=GMT is a list of asteroids by magnitude; Vesta's not at its brightest but is nice and high in Gemini, a degree or so from Pollux so even my skill in navigating the sky should suffice to find it)

Tonight is cloudy, I'll set up the mount indoors with no scope, take the covers off, and try to see if I can see gears grinding. Met Office reckons that Saturday is reasonably promising.

xilman · 2017-03-22, 18:36

Quote:

Originally Posted by fivemack

What are peoples' favourite first-half-of-a-Spring-night objects?

It might be worth finding a double star or few with components bright enough to be easily detectable but not bright enough to saturate the detector too easily and a separation of between 0.5 and 5 pixels. Obviously these criteria are equipment-specific. Sirius would be ideal if it were not for the second constraint, for instance, as the separation is around 10 arsec now (apoapsis is in a couple of years) and the companion is magnitude 8.4.

Given a number of images, sub-pixel stacking and decent deconvolution software you could explore what lies buried within apparently featureless data.

OTOH, a large number of short exposure images of Sirius, each short enough not to be affected markedly by seeing or saturation, may be interesting. Sub-second exposures will (or should, assuming adequate focussing) give diffraction-limited images and the requisite unsaturated images of α CMa A, while a hundred or few should give you easily enough photons to pick up α CMa B out of the noise. The inevitable scintillation and driving errors gives you the sub-pixel sampling for free.

An interesting project? I would certainly like the data-processing challenge but I don't have the optical equipment for this year's apparition.

fivemack · 2017-03-22, 20:41

I set up the mount in the kitchen, plugged in all the cables, and it hummed away happily without making any crunching noises at all.

My suspicion is that the battery I was using had not appreciated being left fully-charged for three months in an unheated building and wasn't producing anything like as much current as the motors expected, and that recharging it for 20 hours made it happier - consistent with this is that, last night, the giant torch attached to the battery was dimming significantly when I ran the RA motor fast.

xilman · 2017-03-22, 20:52

Quote:

Originally Posted by fivemack

I set up the mount in the kitchen, plugged in all the cables, and it hummed away happily without making any crunching noises at all.

My suspicion is that the battery I was using had not appreciated being left fully-charged for three months in an unheated building and wasn't producing anything like as much current as the motors expected, and that recharging it for 20 hours made it happier - consistent with this is that, last night, the giant torch attached to the battery was dimming significantly when I ran the RA motor fast.

Extension cable from the mains supply and an AC-DC converter?

An electrickery expert completed the supply to my proposed observing site yesterday when I was medically detained. I now have four 240V sockets available for drives, computers, etc.

fivemack · 2017-03-22, 21:01

Excellent suggestion; one https://www.amazon.co.uk/GutReise-Pl...S2APTHWB7FDXZ5 (actually the five-amp version) ordered from our dear Amazonian friends

fivemack · 2017-03-25, 09:32

The mount ran happily for three hours last night powered by the 240V-to-12V device.

The current mechanical vexation is that the cable from the intervalometer to the camera is of most inferior quality, and so a fifteen-second BULB exposure quite often comes out as a six-second one followed by a seven-second one - the protocol is one line which you hold HIGH for the duration of the exposure, which does not combine well with poor connections. Perfect Raspberry Pi job, sacrificing the current cable is probably the easiest way to extract the esoteric connector the camera uses.

Polar alignment remains tiresome, and (probably as a consequence) the find-an-object finds them happily to within five degrees - this is fine with a wider-field lens, you can move the brightest star into the four corners of the camera frame to scan a reasonable region and find the object, but for example finding M3 with the telescope was an exercise in futility.

Got Jupiter with four moons through the scope (including a video in which I can definitely see two bands), and with the wider-field lens got reasonable shots of M51, the Leo galaxy triplet with M65, some of the Virgo cluster (which is of course big enough that you'll get some galaxies no matter how bad the pointing is) and M3 with some of the brighter stars resolved. Processing now.

fivemack · 2017-03-28, 06:46

Had some friends round and got out the telescope last night; levelling the tripod with care and a spirit-level turned out to be enough to get goto working much better. Showed them Jupiter, M44 and M45; showed them M3 but it's not really exciting visually; set up the camera and got some OK shots of M3; inside when the corrector plate dewed up.

Much more satisfying experience; Jupiter through an eyepiece with visible bands clearly quite impressed them. Having the mount track the sky makes for a much less frustrating telescope-use-with-guests experience.

2017-03-22, 10:30	#1
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 7²×131 Posts	Equatorial mount is sad First half-decent night for months last night; set up the tripod and the EQ5 mount, put a camera with medium-sized lens on it, turned it on ... and the declination motor made a horrible crunching noise and stopped moving. Managed one usable image (with a 50mm lens, Arcturus across to Denebola catching the Coma star cluster nicely and with a couple of perceptibly non-stellar fuzzy blobs where M3 and M53 should be), using my little portable star-tracker. Then the camera and the astronomer ran out of batteries roughly simultaneously, so I left one recharging with electricity and went in to recharge the other with hot chocolate. What are peoples' favourite first-half-of-a-Spring-night objects? There are the two galaxy triplets in Leo, the globular clusters are starting to come out again (though it'll be midnight before M13 is in a good position); Jupiter is up but I'll need more focal length for him. I think I need a darker sky before trying to do family shots of the Virgo cluster, though the 200/2.8 lens has a wide enough field of view to get some quite good compositions, and probably enough light grasp to get reasonable fuzzy blobs if I can figure out the tools enough to stack sixty twenty-second frames automatically. Last fiddled with by fivemack on 2017-03-22 at 18:16

2017-03-22, 18:11	#3
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 1100100010011₂ Posts	It looks as if a correctly-pointed image with 200mm focal length would get me Amphitrite, Psyche and the M95/96/105 triple all in the same field of view. I think that's worth trying. (http://www.heavens-above.com/Asteroi...&alt=21&tz=GMT is a list of asteroids by magnitude; Vesta's not at its brightest but is nice and high in Gemini, a degree or so from Pollux so even my skill in navigating the sky should suffice to find it) Tonight is cloudy, I'll set up the mount indoors with no scope, take the covers off, and try to see if I can see gears grinding. Met Office reckons that Saturday is reasonably promising. Last fiddled with by fivemack on 2017-03-22 at 18:23

2017-03-22, 20:41	#5
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 7²×131 Posts	Pesky mechanisms and their diagnosis I set up the mount in the kitchen, plugged in all the cables, and it hummed away happily without making any crunching noises at all. My suspicion is that the battery I was using had not appreciated being left fully-charged for three months in an unheated building and wasn't producing anything like as much current as the motors expected, and that recharging it for 20 hours made it happier - consistent with this is that, last night, the giant torch attached to the battery was dimming significantly when I ran the RA motor fast.

2017-03-22, 21:01	#7
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 7²×131 Posts	Excellent suggestion; one https://www.amazon.co.uk/GutReise-Pl...S2APTHWB7FDXZ5 (actually the five-amp version) ordered from our dear Amazonian friends Last fiddled with by fivemack on 2017-03-22 at 21:03

2017-03-25, 09:32	#8
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 7²·131 Posts	The mount ran happily for three hours last night powered by the 240V-to-12V device. The current mechanical vexation is that the cable from the intervalometer to the camera is of most inferior quality, and so a fifteen-second BULB exposure quite often comes out as a six-second one followed by a seven-second one - the protocol is one line which you hold HIGH for the duration of the exposure, which does not combine well with poor connections. Perfect Raspberry Pi job, sacrificing the current cable is probably the easiest way to extract the esoteric connector the camera uses. Polar alignment remains tiresome, and (probably as a consequence) the find-an-object finds them happily to within five degrees - this is fine with a wider-field lens, you can move the brightest star into the four corners of the camera frame to scan a reasonable region and find the object, but for example finding M3 with the telescope was an exercise in futility. Got Jupiter with four moons through the scope (including a video in which I can definitely see two bands), and with the wider-field lens got reasonable shots of M51, the Leo galaxy triplet with M65, some of the Virgo cluster (which is of course big enough that you'll get some galaxies no matter how bad the pointing is) and M3 with some of the brighter stars resolved. Processing now. Last fiddled with by fivemack on 2017-03-25 at 09:41

2017-03-28, 06:46	#9
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 7²×131 Posts	Had some friends round and got out the telescope last night; levelling the tripod with care and a spirit-level turned out to be enough to get goto working much better. Showed them Jupiter, M44 and M45; showed them M3 but it's not really exciting visually; set up the camera and got some OK shots of M3; inside when the corrector plate dewed up. Much more satisfying experience; Jupiter through an eyepiece with visible bands clearly quite impressed them. Having the mount track the sky makes for a much less frustrating telescope-use-with-guests experience.