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Luna-tic

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Posts posted by Luna-tic

  1. I wish I had the head for the higher math, but this has been an interesting discussion. I'm trying to get back in to astronomy after a 3 year hiatus due partially to the pandemic.  We're doing comparisons here to telescopes with a disparity of f/stop and aperture. How does the math work in this instance, with these conditions:

    8" Edge HD with a F/7 reducer, compared to a 80mm refractor using a 1.5x Barlow (in this case a William Optic GT81 which is f/5.9  in its native focal length). Given that the imaging camera is the same for either setup (pick whatever pixel size you want), which would be the better one to image with for deep space objects?

  2. On ‎30‎/‎01‎/‎2019 at 07:26, ejp1684 said:

    I've been using a Leisure battery 20ah for a couple of years now with no issues. Cost £35. After 6 hours observing, including a small heater for the guide scope, it rarely goes below 50% charge when it's still pushing out 12.4v. Built a box for it and secure connections. Key to using it effectively is the electronic charger.

    IMG_1622.JPG.7de852a816fdead0e3c32a790347d98e.JPG

    IMG_1624.JPG.9912cbc415d51c439e1775534b675941.JPG

    Very nicely done power supply, looks great and nicely laid out.. I just finished mine, will deliver 12VDC or 115VAC with included inverter. I'm using a 96 amp/hr deep cycle wet cell lead-acid battery.

    On ‎30‎/‎01‎/‎2019 at 08:49, Carbon Brush said:

    If you choose to carry a big heavy lead acid battery (the cheapest solution) then the type is relatively unimportant.

    In an evening of running a mount you are not going to eat into much of the capacity. So if you have a grotty old battery that won't start the car on a cold morning, or won't hold up the headlights beyond half an hour, it is probably good enough to run a mount. This statement assumes a battery with a general loss of performance through age and sulphate. If an individual cell has failed, that is a different story.

    If weight is of interest, or you are going to have to pay full price for a battery, then you are far better spending on something with a lithium battery.
    Excellent life expectancy. Superb cold performance. Inbuilt charge and discharge monitors prevent you from doing harm to the battery.

    If you want to run a mount, and lots of dew heaters, and a camera, and other things, then you ought to get the calculator out to ensure a small capacity lithium package is going to be good enough.

    Just my take on battery power - not necessarily everyone agrees!

    Hope this helps, David.

    Very true. Generally, the heavier and more basic a battery is, the less it costs per amp/hr. capacity. As you go up in capacity,  up in technology (AGM or Lithium)or down in weight, the prices climb correspondingly. Choose your priorities in weight, technology and capacity, then look at what's out there.

    On ‎02‎/‎02‎/‎2019 at 04:48, Aldebaran5 said:

    if you do the maths, you can work out what you require. A 10amp hour battery will run for 10 hours on one amp. If your unit has a drain of half an amp then it should last for 20 hours, so work out the equivilent usage of all your pieces to obtain the amperage in use. 16 amps will run approx. 3600 watts.

    Keith

    As a very broad rule of thumb, you can figure it that way, but you can only count on about 80% of the total capacity to be useful, and that depends on several conditions. A 12 volt battery delivering 16 amps only gives you 192 watts, according to Ohm's Law, and that is at 0.75 ohms. You'd get 3600 total watts over 18.75 hours at that voltage and load.    Now, if you were at 220VAC and drawing 16 amps, you be using pretty close to 3600 watts.

    A telescope mount of moderate size will draw anywhere from 0.25 to 0.75 amps during tracking. At full speed slew that will increase to 3-6 amps. If that is all you have to power, you can run most of the night on a 20 amp-hr. battery doing observation. I can run a dew heater at full power, my mount, a laptop and two cameras at less than 7 amps total continuous draw. So, for 6 hours, I'd use about 42 amp/hrs. Realistically, it would be longer than that, because the 7 amps is maximum, (during slewing) and drops about 2.5 amps during tracking. Part of the draw is from the inefficiency  in converting 12VDC to 115VAC through an inverter, which part of my gear runs through.

  3. 3 hours ago, Marc2B said:

    BTW, English isn't my native language, I hope you'll forgive my mistakes ;)

    English is my native language, and you're doing a better job than I do most times.?

    Of course, I live in the US South, so our English can be a little.....different.

  4. Can I join the club? My EQ6-R Pro arrived today, along with a Stellarvue FG50 guide scope which I'll install on my GT81. 

    I have an AVX that I really like and unlike some, get good service from. I'll keep it for mainly visual, and grab-n-go service. I may even image with the GT81 on it, but the EQ will definitely get the Edge 8 for AP. Plans are also to use a tandem dovetail saddle and use the GT81 as a guide scope for the Edge.

    All I've done so far is unbox the Skywatcher and put it together, stand back and admire it. I've looked through the Synscan manual, looks like there's quite a few differences (none too serious, though) between it and the Nexstar/Starsense HC's and operations. Hope I get a few decent nights this week and weekend, I'm headed to the Green Bank Star Party mid-July, and want to be familiar enough with it so I don't waste half the night setting it up. One of my clubmates bought one of these mounts a couple of months ago and has been doing some fantastic AP with it and a f/7 102 APO. I fell in love with it immediately; he's going to tutor me in its finer points.

  5. On ‎6‎/‎19‎/‎2012 at 17:33, JamesF said:

    I've read this a quite a few times now in various places, but never with an attribution and I got to wondering if it isn't actually urban legend. The best I can get out of google is this thread on CN:

    http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4784591/Main/4778676

    suggesting that the corrector and primary are not matched, but may be sensitive to orientation and that the primary and secondary are likely to be sensitive to orientation, but it's hardly conclusive.

    I saw that thread as well.

    On ‎6‎/‎19‎/‎2012 at 19:53, E621Keith said:

    From what I read about the process of making Schmidt corrector, I think it's the other way round. Celestron's primary are matched to the corrector plate.

    http://www.oldham-optical.co.uk/Manufacture.htm

    The Schmidt corrector has a very complex curve (looks like at least 4th order), so it will be nearly impossible to grind. Instead the Schmidt corrector is made using a vaccum deformation process. Celestron further developed this using a master mould. I seriously doubt a moulding process can produce a curve as precise as grinding. The final curve will depend on oven temperature, vacuum pump pressure, atmospheric pressure, glass purity and glass elasticity etc... All these variables are extremely hard to control accurately and all of these will affect the final outcome. In fact the article suggest the corrector plate can be a 'few waves' out. As such I believe the primary are made to match the corrector, because it should be easier to grind a spherical mirror to precisely that 'few waves out' than to control all those moulding and material properties variable to give a precise deformation that is at 1/4 wave accurate.

    For mass production, they can make a large batch of the correctors and not very accurate mirrors and test them. Then they can match mirrors and correctors from both groups to find combinations that will cancel out each others error. The fact that the correct need to be line up with the primary in a precise orientation suggest there are astigmatism in both the corrector plate and primary which are cancelled when the plate is placed in that exact orientation.

     

    On ‎6‎/‎20‎/‎2012 at 05:08, E621Keith said:

    I'd think the optical testing procedure would be streamlined or even automated. When I visited the optician, they go through all those test, reading wall chart, wear that funny glasses with interchangeable lens... However, all they really need was that autorefractor machine at the end which can read my myopia and astigmatism in 20 secs. The rest of the eye examinations were to make me feel better having just paid £20 for the test. I think Celestron would have a similar device that can measure the spherical aberration and astigmatism in seconds.

    Also, after the eye test, the optician don't go to start grinding and figuring the spectacle lens (except to make it the right shape to fit the frame), they just go to the cupboard and find the spectacle lenses with matching dioptre and astigmatism that will give me corrections to within 0.25 dioptre. I'd think Celestron do the same for their telescope, they just pick the combinations that will give them 1/4 wave (diffraction limited) or less. You get a very good SCT if the corrector error happens to match the mirror correction exactly, and you get a bad one if the corrector error are near limit of tolerance.

    The one thing the optician can't  do with an optics machine (and it changes the comparison between the eye and a telescope) is measure how the brain is compensating for  visual aberration, and that varies with the individual because part of it is interpretive and can't be quantified.

    I look at SCT manufacture as a compromise between absolute optical perfection  and what someone can reasonably afford. With today's technology, I'd rather have a finely tuned instrument made on an assembly line than a hand configured, although more optically perfect, instrument, because the likelihood of repairing the hand configured one back to its original specs if a major lens or mirror was damaged, is close to nil, without a huge cost involved, both of time and money. The hand configured one will be prohibitively expensive (to me at any rate) to begin with.

    The commercially manufactured ones are of course subject to tolerance ranges determined by by the limitations of the equipment used to make them. So, each and every primary mirror will vary within their tolerance limit, each and every secondary mirror the same, as well as the correctors. The optical qualities of each item can be individually checked by computer, and those computer readouts used to match the items in the most optically "perfect" combinations. When the parts are matched, further fine tuning can be done by hand; this could be as simple as rotating the secondary and /or corrector orientations with the primary once the tube is assembled, to hand grinding/polishing of one or more parts to more closely match them with each other; the degree of which will determine the price range of the item, since the more hand work performed, the greater the cost.

    Even with an instrument that tests "perfect" within the tolerance range of the test equipment, once sold, it will depend on the acuity of the user's vision as to just how good it is. You could have a user with average acuity and a telescope where everything fell precisely into place, and said user could not fully appreciate how good his scope was. You can also have someone with perfect vision and a perfect scope, and how they rave at the quality of the views they get; there's also the guy with perfect vision who happens to have the scope at the lower borders of the tolerance range, and how they complain that they'd never buy another product of that company, as well as a guy with poor vision and a poor scope, who can't see anything.

    Consumer products aim at price points and they are built to provide a level of quality that matches that. The better you want, the more it will cost; a level is reached where the cost is prohibitive to the point of nobody buying it and no manufacturer will approach that. Can't make a living that way.

    • Like 1
  6. On ‎12‎/‎10‎/‎2017 at 06:38, GalileoCanon said:

     If I'm not mistaken isn't a 50mm lens pretty close to what the naked eye sees? If I hold my camera to my right eye with a 50mm lens isn't that pretty close to what I'd see in size if I looked at the image directly with my left eye?

    Pretty close, I think, except your eye will give a much wider FOV with peripheral vision, but your central vision would be close to what a 50mm lens gives. I think that is why 50mm is so commonly used for standard prime lenses.

    On ‎12‎/‎10‎/‎2017 at 06:51, Ouroboros said:

    Maybe you've said but what sort of DSLR have you got? 

    Not sure if that was directed at me(with all the quotes flying around:icon_biggrin:), but my D3400 Nikon has a crop sensor.

  7. "Magnification" is all relative to a baseline size. I think you're asking "how much bigger will the picture image look at prime, versus naked eyeball, and telephoto lens at XXmm ". All I can do is give some comparative photos which might give you an idea. You'll have to consider the focal length of the telescope used; at "prime" focus, it would be like having that focal length lens on the DSLR. In my case, the telescope used for comparison has a focal length of 2000 mm.

    1st picture: Nikon D3400. 18mm lens, 1/4 sec, f/3.5 at ISO3200     Same camera used in all pictures

    2-Nikon D3400. 300mm lens, 1/4 sec, f/6.3 at ISO 3200

    3Nikon D3400. EYEPIECE PROJECTION, Edge HD 800, 25mm EP (40x magnification) 1/160 sec at ISO 100

    4-Nikon D3400. PRIME FOCUS, Edge HD 800 (2000mm F/L) 1/60 sec at ISO 400

    See the relative difference in size of the Moon? Frame size is the same in all four photos. These were all taken the same night, so relative Moon size is the same. This was last week's Supermoon from the SE USA.

     

    DSC_1016.JPG

    DSC_1017.JPG

     

    DSC_0949.JPG

    DSC_0931.JPG

    • Like 2
  8. 1 hour ago, deepind said:

    HI All,

    I have nikon d3200 , is it good for astrophotography? i tried with 18-140mm lens but the shots are too much white not good..do i need to upgrade to d3400 or d5300 or d5600?

     

    Try these settings: auto white balance; MANUAL mode, aperture open as far as the lens will go, focus at infinity; ISO 1600, shutter speed varied from 5-25 sec. Mount on a tripod and use a remote release. You can experiment by varying ISO and shutter speed, but something along those lines should get some images, if light pollution is not too bad (sky looks black). If the picture is still washed out at lower ISO and faster shutter speeds, you're probably too light polluted.

    I have a D3400, it's just the latest version of your D3200 (with the D3300 in between). I get great results with the pictures I'm taking.  If you plan to step up, go at least to the D5600 or D7500; the D500 is the top of the DX line.

    Canon seems to be the go-to for astrophotography, you may want to look at some of their offerings.

  9. I am so envious. I spend a lot of time around Orion, but the seeing here, mainly due to LP, just won't let me see much other than M42 and 43. Even trying for a 20-30 second exposure at ISO 6400 won't give me much. Night before last, I got just enough of the Flame to make out the general shape, with a 45 second exposure. Forget visual (Edge HD 800 and 25 and 40mm EP's), it just wasn't happening.

    Great post, I felt like I was there.

    • Like 1
  10. 12 hours ago, sophiecentaur said:

    Thanks for the replies. Fact is that I am getting older and I can't be sure that I won't be infirm if I wait too long. Sob sob.

    By 2028, I may have no idea who I am or where I am. lol So I want it to be fairly soon. Patagonia has serious appeal, though. It's well off the beaten track. Lovely shots of the Solar Eclipse, BTW :happy7:

    I thought that might be the case. I'm getting there, too. I'll be 70 in 2024, hope I'm not blind, or worse, by then. Maybe the old-folks' home will have an excursion so I can go see it (2024 eclipse). Maybe I can design a clamp to mount my telescope to my walker for the occasion.

    Patagonia that far south is so far off the beaten track you can barely see it from there. Never been there myself, but from looking at Google Earth, it's just one step removed from the Moon. My daughter has been to that part of the world (works on a cruise ship), she says that southern Chile is nice, at least the areas along the coast she's seen, but southern Argentina is pretty desolate.

    Certainly it would be an adventure to go there, eclipse or no. Hope you can work it out. Here's a couple more shots I made, to further whet your appetite:

    solar eclipse 8-2017 Bailey's Beads at 2nd Contact (2).jpg

    Solar Eclipse 8-2017 Diamond Ring.jpg

    • Like 1
  11. Are you particularly wanting to see a total eclipse in South America (once in a lifetime trip), or just wanting to see a total solar eclipse?  The terrain in that part of South America east of the Andes is pretty much desert. The Argentinian coast from Viedma to about 30 miles south of Las Grutas might be the only decent area in Argentina to view. West of the Andes is a bit greener and more populated, although that's a relative term. Only three cities of note in Chile in the path of totality: Temuco, at the northern edge of the path, about 262,000 population. More in the path center are Nueva Imperial, population 29K, and Petrufquen, population 21K. My choice would be somewhere near one of those cities, or along the Chilean coast from Isla Mocha to Nueva Tolten.

    If you want more viewing options for a total eclipse, why not wait to 2024 and come to the States? Longer period of totality, much, much longer path to choose a site from.  And English is (sort of) our first language.

    I was only a 2 hour drive from the path of totality back in August; I'll have to drive about a day to get to the one in 2024, but I plan to be somewhere in the path. Took these shots through a C6 back in August.

    solar eclipse 8-2017 mid point to totality.jpg

    solar eclipse 8-17 totality late.jpg

    • Like 2
  12. On ‎10‎/‎28‎/‎2017 at 14:03, newbie alert said:

    Orion is pretty bright..you can get a decent image from very short exposures..its said that is one of the easiest and difficult nebula to image because of its extremes of the dynamic range..easy to over expose the core (trapezium) but long exposures are better for the outer dust.... hense why the experienced use different subs lengths  and merge them together..

    Whatever you do you will get a image..and when the first one pops up on the back of the camera I bet you have a grin from ear to ear..

    Exactly. Because it's bright, it's one of the first DSO's people try, and why I also tried it. Stacking and processing is the only way to get even lighting and a full image of it; I knew that going in, but I'm taking 'baby steps', looking at exposure times and ISO to gauge tracking accuracy without guiding (I'm using a long F/L scope). I took over a dozen images of M42 at exposures from 20-40 seconds and ISO from 1600-12800. It's easy to see in the combinations where tracking becomes an issue and noise starts becoming prominent and where lighting is enhanced or inhibited.  I've also played with less-bright objects like M1, M31, M13 and some of the open clusters. Once I get a feel for this, I plan to start stacking images and playing with them in Registax and Lightroom, using filters, etc to improve coloration and visibility.

    Now that I've photographed a rather large-field DSO, I know what to expect with FOV and my longer F/L and a DSLR's sensor size. Hopefully, Celestron won't take the remainder of my lifespan to get their reducer availability issue worked out. Then I can open up my field a bit. Fastar and f/2 is further down the road.

    As for the grin, I still have it, several days later. This is FUN.

     

    • Like 1
  13. I'm in deep envy of all those shots. I've been making a few attempts at single images, haven't gotten serious enough yet to start stacking, but I'm getting there.  

    The 1st pic was a couple of weeks ago, M13, Don't remember offhand the shutter speed or ISO It's an EPP attempt through a 13mm 65* FOV EP. The rest I did this past evening. M103 and M36, ISO 1600 at 30 seconds. 1st M42 at ISO 1600, 32 seconds, 2nd M42 32 seconds at ISO 12800. All single exposure, Nikon D3400 at prime on Edge HD 8"/AVX. I did around ten images at different shutter speeds and ISO on M42, obvious that you can't get much of the nebula without washing out the center; getting the Trapezium clear gives you little of the nebula. Hopefully I'll improve as technique gets better.

    M13 Hercules Cluster 10-17.JPG

    M103 cluster.JPG

    M36 cluster.JPG

    DSC_0788.JPG

    DSC_0782.JPG

    • Like 2
  14. 18 hours ago, matt_baker said:

    I was wondering what exposure time and iso I should use to capture the Orion Nebula. I have a Celestron 130SLT and a Nikon D3200. I know that this isn't necessarily the best, especially for astrophotography but I did give it a go before and I want to try and improve on the results that i have right now. Here's an example:

    Thanks,

    Matt

    P.S I took 19 light frames and stacked them on autostakkert and did some things in photoshop

    10414b1dfcc2d0e8357708b01de61647.jpg

    Nice picture. Based on what I did tonight, I'd agree with ollypenrice. The heart of the nebula seems to capture well with relatively short exposures, but the outlying parts need longer exposure to bring out the details. I was out tonight, just got in two hours ago (5am EDT)and played with my setup to see what I could get on several objects, primarily M42. I bracketed ISO and shutter speeds, trying to see what the best combination was. High ISO (12,800) tends to wash out the heart and induces a lot of noise at 32 seconds. I kept dropping ISO and kept exposure times around 25-30 seconds, finally getting to ISO 1600 at 32 seconds. 

    1st image below is through a Edge HD 8"  on AVX mount with a D3400 at prime, single exposure 32 seconds @ISO 12800. 2nd image is single exposure 32 seconds @ ISO 1600. I shot both RAW and jpeg, these are the jpeg images. They've been cleaned up a little with contrast and brightness adjustments, but not much, and the red has been slightly enhanced.  I haven't started stacking images yet, but given my results tonight, am going to start soon. These are first attempts at DSO AP.

    DSC_0782.JPG

    DSC_0788.JPG

    • Like 1
  15. 6 hours ago, Droogie 2001 said:

    This sounds very much like the issue I have / had. When I first got the mount the issue was not present but then one evening it started occuring for no apparent reason. If I rotate the DEC head the counterweight bar / weight would not rotate at the same rate meaning they would be left off centre. I have included the video below that I sent to Celestron to demonstrate the issue, is this what you are experiencing?

    After many different ideas with the vendor it went back to Celestron. They could not see the problem and low and behold when I got it back the issue was still there...:hmh:
    Tried different counterweight shafts and different 'Black Collars' (AKA Flowerpots). I can see a scoring inside the flowerpot so it seems to be rubbing on this.

    The only way I solved this was to remove the collar (flowerpot) as my mount is well out of warranty, its not needed and is simply there for cosmetic reasons. Not something you want to hear on a brand new mount I suspect?
    I would suggest arranging a replacment if it is brand new as I have never found a solution to this...

     

    AVX_DEC_FAULT.mov

    Someone on CN posted a similar issue and a respondent asked for pictures to show where it was occurring, to clarify things. I had done some experimenting after my last post above, and determined the "steps" in the counterweight rod cap and the "steps" in the mount housing were interfering due to insufficient clearance. I placed a 3mm thick washer in the bottom of the cap, and it fixed the issue by making a bit more room between the surfaces of the interfering steps.

    DSC09941_LI.jpg

    DSC09944_LI.jpg

    DSC09945_LI.jpg

  16. On ‎6‎/‎1‎/‎2016 at 07:34, PeterCPC said:

    Louise

    When I regreased the cog wheels on mine I used Lubriplate 105 as I saw that it was recommended on here in other posts and Paramount use it apparently. It's a bit sticky.

    Peter

    I wonder if Lubriplate 130A would work? Not sure how the consistency compares to 105, but it sure does well in my firearms. It's about like a heavy pudding, is Teflon based and doesn't get slung off the rollers or bolt carrier on the semi-auto rifles I use it on. I've never had it to dry out on a stored gun, either. It feels light enough that it wouldn't create drag on a slow moving gearset, but it has a great lubricity.

    All this talk about AVX repairs has me a bit worried; I just bought one, all the advertising hype sounded good, and it was affordable. I have noticed, however, that when I assemble mine, specifically when I screw in the counterweight shaft, when it is snug, it creates a drag on the Dec axis. If I release the clutch and manually rotate the Dec axis, the counterweight shaft will loosen just a bit, and the axis is free, with little resistance. I have played with it several times and can't really pinpoint where the binding occurs, such as if it's the black collar and how it fits around the base of the mount body, or whether the shaft itself bottoms against something in the threaded hole. I plan to add a small washer in there and see if it will then tighten without binding. Anyone else have this issue? I was sort of surprised that the counterweight shaft rotates with the Dec axis, my (smaller and less heavy) last mount did not do this.

  17. 2 hours ago, celestron8g8 said:

    Been knowing what you said for the last 25 yrs . But what is your point , are you not understanding or are you just adding to what I already know but didn't mention ?

    Even though I quoted you, it was more addressed at the OP, maybe he didn't know, since he's asking about diameter.

  18. On ‎8‎/‎30‎/‎2017 at 16:38, celestron8g8 said:

    12" would be nice but if too big for you go with a 10" . Aperture is your friend just for observing . 

    Aperture increases brightness and resolution (detail). Don't consider  the difference in aperture diameter as much as the difference in area of the mirror, which increases as a square function of diameter. My C8 collects almost 45% more light than my C6, from a "mere" 2 inches difference in diameter.

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