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| Night Sky Photography - Page 4 | |
| An Equatorial Mount: My lucky day! | Rate Topic |
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| Posted: Sat Mar 16th, 2019 09:12 |
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31st Post |
Robert
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It seems to be moving slightly but there seems to be a window of about six hours of almost clear skies.
____________________ Robert. |
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| Posted: Sat Mar 16th, 2019 16:39 |
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32nd Post |
jk
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Lots of flooding up North take care!
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Sat Mar 16th, 2019 17:19 |
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33rd Post |
Robert
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Thanks JK, Just been looking at the news, they have called off the three peaks race due to flooding. I will be at about 350 Metres (about 1,150 feet), but I do have to pass through Broughton Mills, a tiny hamlet with a very tight bridge, a square bend off this tiny narrow hump back bridge, then it goes down to beck level. If I am going to have a problem it will be there, although there is a splash well up in the hills where the road becomes a river for 50 yards. Onto the road through one field gate and back off the road through another field gate. I have seen it a foot deep through there. It will all be gone by tomorrow night. Seathwaite has the highest rainfall in an inhabited area in UK over 24 Hrs and is about a mile from where I go for my night sky photography. Seathwaite Farm, Cumbria, November 19 2009 – 314mm* Martinstown, Dorset, July 18 1955 – 279.4mm Bruton (Sexey's School), Somerset, June 28 1917 – 242.8mm Upwey (Friar Waddon), Dorset, July 18 1955 – 241.3mm Cannington, Somerset, August 16 1924 – 238.8mm Loch Sloy Main Adit, Strathclyde, January 17 1974 – 238.4mm Long Barrow, Devon, August 15 1952 – 228.6mm Upwey (Higher Well), Dorset, July 18 1955 – 228.6mm Bruton (King's School), Somerset, June 28 1917 – 215.4mm Timberscombe, Somerset, June 28 1917 – 213.1mm Rhondda (Lluest Wen Reservoir), Glamorgan, November 11 1929 – 211.1mm Upwey (Elwell), Dorset, July 18 1955 – 211.1mm Kinlochquoich, Highland, October 11 1916 – 208.3mm Camelford, Cornwall, July 8 1957 – 203.2mm Bruton (Pitcombe Vicarage), Somerset, June 28 1917 -200.7mm Wynford House, Dorset, July 18 1955 – 200.7mm Otterham, near Boscastle, August 16 2004 – 200.4mm * Figure recorded by the Environment Agency There are many recorded high amounts of rainfall in the West Country.
____________________ Robert. |
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| Posted: Mon Mar 18th, 2019 12:01 |
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34th Post |
Robert
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Well the six hour window collapsed into two much shorter sessions. Nothing exciting materialised except I became slightly better at setting up! I have yet to analyse the images but the last set with my 16mm fisheye seems pretty reasonable. The main thrust if my efforts were to assess the improved alignment of the polar scope, I think it's much better but key to this will be a new solid and adjustable base mount to fit on the tripod and to mount the polar rotary tracker in very accurate alignment with the celestial North Pole. I have reached the drawings stage, I need to design the details of the adjustments and somehow devise some method of locking the adjustment robustly but without imposing great stress on the mount which will cause it to move out of alignment, the adjustment is extremely fine, accuracy needs to be in the region of 5 arc seconds or better, that means you can barely touch it because even a very heavy tripod will flex that much easily. It really needs bolting down, to something very solid. I do have ideas.
____________________ Robert. |
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| Posted: Mon Mar 18th, 2019 12:27 |
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35th Post |
chrisbet
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Just an off the wall thought - if you need something that remains perfectly in alignment with the earth's axis, would some sort of gimbal work?
____________________ If it is broken it was probably me .... |
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| Posted: Mon Mar 18th, 2019 12:52 |
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36th Post |
jk
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Robert, it is now illegal to use child labour so no sending the boys up mountains with predrilled slabs!
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Mon Mar 18th, 2019 15:10 |
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37th Post |
Robert
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LOL, what about a generator and rock drill? A helicopter would come in handy...
____________________ Robert. |
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| Posted: Mon Mar 18th, 2019 15:23 |
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38th Post |
Robert
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chrisbet wrote:Just an off the wall thought - if you need something that remains perfectly in alignment with the earth's axis, would some sort of gimbal work? It's getting the alignment which has to be pretty exact with basic and robust design. Something like a Wimberly might be OK for the articulation but it has to be rock solid, Wimberlys are not rock solid. The head I have is supposed to have a 5 Kg payload, but the payload is supposed to be balanced so the motor doesn't slow down uphill or speed up downhill. Speed has to be consistent 1 revolution per 24 Hrs. The 300mm lens and D800 weigh about 2.5 Kg so it needs about a 1.5 to 2Kg counterbalance, less then the camera/lens, because it can be hung out on an arm so you get the right leverage without adding too much to the payload. The design is coming together, I am tempted to make a wood mock up to avoid making a metal one which has a snag. Just about to process last nights images, this will be interesting...
____________________ Robert. |
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| Posted: Mon Mar 18th, 2019 15:52 |
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39th Post |
jk
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Looking forward to see those images. I am sure it will be a big improvement. Problem is that further improvement will be a lot of work for just inch-pebbles. Per ardua ad astra!
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Mon Mar 18th, 2019 18:19 |
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40th Post |
Robert
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Here you are JK... Please bear in mind these are not intended to have artistic merit, they are simply the results of experiments and an attempt to learn how to set up an Equatorial mount for photography. I am learning and making gross mistakes. These images were made with a Vixen EQ-polar mount and a D800 with 70-300 lens and 16mm f/2.8 fisheye lens. They were 25 second exposures taken at 26 second intervals - one second gap. The black spot right of centre must be a spec of dust on the sensor. The first image was made without the Vixen mount motor running, about 40 exposures. The bright star to the left near the centre, is Polaris. You can see how far it is from the celestial polar centre.  This was taken after the initial 40 exposures, I switched the motor on but the setup must have been very wrong. I think I rotated the polar locating scope the wrong way, I was trying to get Ursa minor aligned but somehow I missed!  This is the two above images in one.  Finally back to Stickle, only a short session with the fisheye. 74 images stacked. Notice I am much nearer the correct polar centre. Again, 25 second exposures at f/4.0 for some reason only ISO200, I must have forgotten to re set it for astro, I usually run at ISO 1600. I need to sit down and set up some dedicated menus for astro photography. 
____________________ Robert. |
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