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Geoff Lister

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About Geoff Lister

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    Star Forming

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  • Interests
    Railways (full-size and model), radio-controlled model boats, and astronomy
  • Location
    North Somerset, UK
  1. Geoff Lister

    Dobsonian Focus messed up

    It is still worth doing another check around the area where your son "didn't" dismantle the focuser. The other area to check, is that it did not fall down inside the lower section of the tube. An unattached screw can do nasty things to primary mirrors. Geoff
  2. Geoff Lister

    Dobsonian Focus messed up

    Yes; there should be a grub screw in the centre hole. It presses on a block incorporating a Teflon pad, which in turn presses the focus-adjusting spindle on to the underside of the main draw-tube. Your symptoms indicate that it is indeed likely that the grub screw is missing. Geoff
  3. Yes. They are both good. On paper, the Heritage 130P is the simpler, in terms of off-grid portability, but the mount is an odd shape for packing. For portability, I have found the Skymax 127 with Synscan mount is very robust. A Porta 2 will give you a manual mount, but I have found the Synscan GoTo a pleasure to use, and the planet tracking works well at high magnification. The whole setup, below, with a few eyepieces and 2 sets of batteries, weighs under 11kg. I liked mine so much, that I bought a second one for my holiday home in southern France (OTA in hand-luggage, the rest in a wheeled suitcase). I have not had to adjust the collimation on either Mak. OTA, but I did with the 130P Newt. These are my power sources. For portable use, I tend to prefer the pair of the 6V NiMH packs, borrowed from my radio-controlled model yachts. They give me a good evening's observing before needing a re-charge. I tend to use my 32mm Plossl for initial GoTo alignment, and for viewing the wider DSOs. The 130P OTA will fit on the Skymax mount if I want a wider view. The 127mm Mak is excellent for planets. I, too, was concerned about the 130P's helical focuser, but, because the focus tube is at the top, the weight of the eyepiece keeps the thread nicely engaged. I tried PTFE plumbing tape, to make it a bit stiffer, but the tape is designed for a one-time-only compression fit, and I found that it was being slowly shredded as I used the focuser, so I took the resulting little bits out. It works with zoom EPs, provided that you grip the focuser whilst adjusting the zoom. Geoff
  4. Geoff Lister

    Helical Focuser question

    I fitted the same Lacerta retro-fit unit to my 10" Dob. It was easy to change and makes focus much easier at higher magnifications. Geoff
  5. Geoff Lister

    Celeston Starsense

    I've got Starsense built in to my Skyprodigy mount. It works well when it is dark (even with moonlight) but it needs to see tens of stars in several small patches of sky. Around the summer solstice, most of the UK does not have astronomical darkness, and, certainly in the Bristol area, you are lucky to see more than a few of the brightest "Alpha" stars much before 23:00. However, by using my Skymax mount (mechanically equivalent to the Skyprodigy, but without the camera), with the Synscan "Brightest Star" alignment, I can start with a manual slew to Jupiter and then automatic slews to Arcturus followed by Altair. This gets the mount aligned, and you can spend plenty of time enjoying Jupiter whilst waiting for the faint fuzzies to become visible. Geoff
  6. Hello Chris, As has been mentioned on various previous threads, the battery design for vehicles is based on a short burst of high (starting) current followed by an almost immediate recharge as soon as the engine picks up. The best batteries for mount supplies are the "leisure" style, designed for caravans and the like, where a longer period of modest discharge is to be expected. Although the headline capacity may be the same, the internal plate design is different, and with different proportions of the active compounds. Geoff
  7. From my understanding of the handset/mount interface, the circuitry is designed round 3.3V TTL and not the sort of robust, balanced, Ethernet-style interface. The longer the cable, the more the transmitted pulse shape and amplitude will be degraded, to the point that the receiver will not change state, and this is most likely to show up as intermittent operation. Additionally, you are less likely to trip over a short cable in the dark. Geoff
  8. I did some measurements on my mounts, so this may give you a rough idea Geoff
  9. Try "RJ12 extension cable" in a search engine. I added an RJ12 coupler adaptor block and 1m long cable to the handset on my Skyprodigy without any problems. Just make sure that you get the "6P6C" versions, as there are also similar RJ11 adaptors/leads, (often labelled "6P4C") but with only connections on 4 of the 6 possible positions.
  10. Geoff Lister

    Skywatcher 127 matsukov

    My 127 Mak gets used at least as much as the combined usage of all my others.
  11. Hello muletopia. The Sitech User Manual (difficult to view from the site) states "Will last several nights on one 7 amp hour Gel Cell on most telescopes." Assuming a 12V battery, that means a 84 watt-hour supply, but used over several nights (assume 2 off, 12 hour nights, as a worst-case of "Several"), this is a continuous power consumption of about 4W. From my understanding of the manual, this is based on a typical mount with a mix of a bit of slewing and mostly tracking. Now, assuming that you do not want your pair of 70 Ah batteries not to drop below 50% charge, (35 + 35)Ah * 12V /4W, gives at least 210 hours (at 168 hours per week), before the clouds clear. Once they clear, you should have 96W from your panel to recharge the batteries. Very much a "back of an envelope" calculation, but it may help. Geoff
  12. Geoff Lister

    I must be blind

    Hello, and welcome to SGL. Good advice, above, about checking the alignment of the finder. A X2 Barlow lens will turn your 25mm & 10mm eyepieces into 12.5mm and 5mm. I use my 32mm Plossl as my initial eyepiece for finding the object, and then increasing the magnification until the contrast starts to suffer, this is particularly important with the 3 planets close to the horizon. The Celestron 24-8mm zoom is good value and, with the X2 Barlow, would give you a range of 24mm to 4mm. One big advantage of the zoom is that you can increase the magnification until you hit the magnification / contrast sweet spot for the viewing conditions. At the 5/4mm end, you are going to be doing a lot of nudging to keep the object in the field of view. If Demonperformer has identified your 'scope, you will have the option of 2" eyepieces. For the time being, I would suggest keeping to the 1.25" ranges, but in the future, you may want to get something like my 55mm Plossl for wide-angle views (in my case, very rarely used, as the 32mm 1.25" is fine on most occasions). Geoff
  13. Geoff Lister

    Hello from South Bristol

    It was an idiotic move, naming a county after 4 English and 2 Scottish rivers. There are still some databases that add "Avon" to the delivery address, when you submit your postcode; and the local constabulary have yet to ditch the "Avon" bit. At least the district of "Woodspring" seems to be dead and buried.
  14. Geoff Lister

    Hello from South Bristol

    Hello Bovski, and welcome to SGL. I live in North Somerset, and visited the BAS's Failand observing site last year. One of the SGL moderators, @John, is a member of BAS, and we met during that visit. Clear skies, Geoff
  15. Geoff Lister

    Biggest thing you can fit on a virtuoso mount?

    The Virtuoso mount will take both the 127mm Mak., and the Heritage 130P's truss-tube Newt. I have tried, and used the mount with both. However, as both are longer than the 90mm Mak., if they are mounted so that they are balanced in the dovetail clamp, the Mak's diagonal/Newt's rear plate will foul the azimuth axis clutch adjustment knob at high altitude angles. There is a solution to view high altitude objects without putting too much strain on the mount. It is possible to move both forwards (effectively upwards)in the dovetail clamp, to clear the rear obstruction. With power still ON, the mount will still keep tracking alignment as you make adjustments in the dovetail clamp and the altitude clutch. The other consideration is the overall mass and moment-arm of the larger OTAs. The Virtuoso mount has a much higher maximum slew rate than the Skymax's tripod mount. This is not a problem with the light, short, 90mm, (1.3kg, I believe) but the 127mm OTA with finder and eyepiece is about 3.5kg. The Virtuoso mount's slew speed starts at maximum (level 5) by default, but can be reduced by pressing buttons "4" or lower. With the heavier OTAs, even when balanced, I do not go faster than "4". In most cases, this is not a serious restriction, as you can release the clutches (holding the, possibly, unbalanced OTA), point in the rough direction of the desired object, tighten clutches, and then use the buttons, at lower speeds, for final alignment. I would not fancy dismantling a Mak., drilling holes in the bare tube, and then re-assembling and re-collimating. If the finder is in the wrong position, it may be possible to mount the OTA facing south, and do a southern hemisphere mount calibration. I believe that this keeps the tracking's azimuth component, but reverses the altitude component. Geoff

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