SimM

The video is from the main imaging scope? What you see are called "cone errors". They are where any scope is not completely at right angles (perpendicular) to the declination axis - you might think of this as "around" the RA axis. For the main image, you might try rotating the dovetail in the mount 180 degrees - it might seat better? Or swapping the rings front to back. Or putting shims under one/both/most corners of the rings (where the y bolt to the dovetail). However, in the HEQ5 HC there is an alignment to remove the effects of cone error - all scopes will have this to some extent? With a 3 star alignment the extent of cone error is known and compensated for. What you see is independent of where Polaris is in the main scope. To do PA with the polar scope, you don't even need the main scope to be attached? Separately, if the image in the polar scope is also moving, then half the error (which isn't cone error) can be taken away by referring to the manual and carefully centred with three small grub screws. If the clock display isn't at 12 o clock this can also be corrected - but isn't necessary as you already know where 12 o clock is on a clock without numbers? This stuff is in the manual. There is a newer graticule display that's not mentioned in the manual - is on an addendum sheet. Simon

Thanks for the info James, 600 cubed is about 0.22m3 or about 425kg. Can that be right? How many bags of mix did you use? Postcrete or ready to make concrete (about 16ish)? Slightly different, I thought about using a similar volume to make a concrete base the area of my tripod x 200mm to stand on a base of sand. Obviously not permanent as a pier, but a good/bad idea? Simon

Hi John I would agree with you that it's difficult to reach a conclusion. QHY OAG has an 8mm prism (small/medium and large OAG have same prism), ZWO has a prism/mirror also 8mm (but has only a limiting 5mm aperture) and Celestron has a 12.5mm prism with a limiting lower prism height. ZWO also uses a dovetail like Celestron but it's not 360 degrees - some users get flexure as a result depending upon the weight of the camera used. Bigger is always better? Probably true with many mounts and also for prisms. However, there is a point reached where the prism interferes with the main image - do you want the prism to be closer to on-axis but also provide a reasonable "view" for the camera? For 174 the sensor is too big for QHY or ZWO OAGs - better for 178 or 290.I have a 178 as a guide camera 5x7mm sensor. 17mm height of the COAG is just too close to the diameter of the back of the 800 0.7x reducer, so limited view and poor image quality. For the EdgeHD 800, the image circle from the Reducer is 26mm - so being at 34mm diameter is a big "ask" and can get closer with a smaller prism. I also wanted to use my Baader ClickLock for visual/AP switching and to keep one BF behind the prism e.g. one setup across all scopes (no refocusing of the GC). Simon

Just received QHYOAG-M and some M54/M48 adapters. Thickness of the OAG is 2(1.5 + 3)+10= 19mm. An 8x8 prism + 7.5mm clear aperture. EdgeHD 800 0.7x Reducer has 26mm image circle with 35mm objective (In comparison, Celestron OAG had minimum prism centre height ~17mm). I want the prism centre height to be 12mm - 14mm above the central axis with minimal OAG spacing after the prism (think F/7 cone of light to the main sensor). I have to do setup in daylight with M48 extension tubes and test operation with clear skies later. Guide camera is QHY5III-178M with 2x2 camera binning. Simon

1m3 or 0.7m3 is a lot of concrete to buy/mix up by hand is a lot! A pulsar dome has a suggested base with a block of concrete 1m x 1m x 0.7m with a separate 150mm deep base for the dome around (but separate) from the pier. That's about 2m3 - enough to consider having concrete mixed and delivered (about £250). I don't think I would risk leaving a mount permanently outside. Screwfix have a British General (BG) double socket for outside (with/without RCD) for £30/£10. I have one on an outside double BG socket on a wall overlooking my patio. It looks very neat and has clips to close and seal over the sockets and also for the plug cables. There is space to add a lock if required. I was considering using one (with the sockets removed and replaced with a cover plate) to make a waterproof access point (junction box) on the side of a future pier. I was also considering a 100-150mm thick slab of concrete of about 1.2m diameter (TBD) to stand my tripod (0.85m leg-leg) - as an alternative to 3 x 45cm pavers currently setup in a "trial" location on the lawn. Simon

Todmorden Pier was the name I was trying to remember. I bought two of the concrete hollow blocks and can construct the upper portion. That's when it starts to be uncertain e.g. jut how much concrete is required to ensure it's stable (I'm mostly on a sandy soil). I can see that a pier provides a repeatable process e.g. helps with PA etc. but I also wanted to know how much of an improvement it is e.g. is a steel mount an issue that the blocks fix? Is having a steel brake disk any better than wood? What properties are important etc. ? I'm reading a book on AP that shows a metal spike/bar, driven into the ground, with a nylon plate (to locate it) and an Allen bolt (for the spike to stand on). Seems a good idea, but I wonder if the spike is stable enough e.g. I know that only a slight change in position introduces a change in alignment? One thing I noticed with using the pavers (round concrete) is that after only a few weeks, they bed down and start to be part of the lawn and no longer rock. I'm tempted to glue 3 washers to help with repeating polar alignment and see how that goes but my feeling is that a slab of concrete is the way to go. Just because it's simple doesn't mean I need to get it right e.g. to improve what I have. Al least I understand the drinks holder concept. Simon

I guess what I was trying to show was something like: do a star alignment, return to the star(s) used in the alignment, wait and repeat. At the very minimum, you would expect the mount to return to the alignment stars. Like all electronics, if you change something then you look back for the change e.g. replaced a cable, swapped one PSU lead for another etc. and try to put it back to the before state. An EQDir cable has a USB at the computer and the mount connector (serial) at the other end. In windows you can choose the speed of a serial lead - a mount doesn't need a high speed to be effective. Even a speed like 9600 baud is worth using to confirm it works OK. Most cables will use the same serial port and hence the same settings e.g. COM3: etc. But it sometimes changes e.g. a 2nd computer USB port can result in COM4: If you are using a laptop there may be an always on port e.g. I have one that will not recycle as the laptop is switched off or rebooted - for some things this makes a difference. My second port will get recycled which helps with some devices that expect this. Have you switched ports? Changed cables? The length of the cable shouldn't be too important because after the connector, it becomes a serial cable and these can be up to 30m especially if you don't expect it to run too quickly. One issue with electronics is a ground loop. If you haven't changed too much then this shouldn't be an issue if it wasn't a problem before. Simon

It is unlikely to be the cable if you are not actively sending a GOTO command. However, in Windows there is an option to control the speed of the serial port - have you tried setting it to 9600 baud (or even 115K baud). Some mounts have a serial port connection or a USB port that's connected to a serial port e.g. not directly accessible. HC is a serial interface. When you say it goes to the wrong location, is it always or only sometimes? Perhaps you have tried a 2 star alignment and then returned to either of the named two stars, as well as somewhere else? Immediately and later? Simon

Has anyone tried a mount like Stacey's pier (Astrostace YouTube): https://www.youtube.com/watch?v=Pg7QlsOlNEI Her introduction to piers: "So, does anyone else have a pier that has an inbuilt coffee/beer holder and a built in guard system? ". I do wonder if the blocks are more rigid than a steel tripod - if it's on a firm (concrete) pad? I could produce a hardwood pier adapter as an alternative to getting a steel/aluminium one - benefits? Simon

I'm, not a fan of the SkyWatcher coiled lead from mount to the HC - as it will always be in tension if you hold the HC. Have you tried a CAT5 Ethernet cable as an alternative? In the Utility menu you can check Information like the voltage at the mount? It doesn't update so you have to exit and return to see an update. It may be less than you were expecting? Does it go awry when you slew or after tracking at sidereal? At speed 9 or 5? For signalling a USB2 cable has a range of about 5M whereas a USB3 cable is less e.g. 2M, so USB 3 is higher speed but less range e.g. not always better. Simon

If you align with the HC then only the HC knows where it is. The mount doesn't know anything about where it is and the HC is acting like your computer. So plugging the mount into the computer instead of connecting the HC to the mount, means that you have to start again. Simon

Better or worse?

A 10mm thin OAG is just the OAG throat with an adjustable prism and possibly a focuser. That's good, because you can add t- adapters et.c each side to get the required setup and BF. I'm finding it hard to get a decent spec. on any of the available (and not to specialist/expensive) OAGs. They don't seem to do a good job at detailing the available movement of the prisms and what the BF behind the prism is. By only concentrating on the total BF for a camera e.g. when using a DSLR, they neglect to say important details about the range of adjustments on the OAG for the prism. Since the BF is common to both cameras, it needs more information about the prism adjustments to allow selection and operation of the OAG. As an example, if you don't know the range of prism height adjustment available, then you can't be sure that the prism can be moved into and out of the way of the main sensor, especially when the available depth of the guide camera has to be considered before adding extension tubes between the OAG and the camera, which will effect how much the prism interferes with the main sensor. Simon

With your flattener/reducer you simply want the “wide” T-Mount for your camera with M48. Canon, Nikon and others, have a flange to sensor distance that varies slightly but is around 44mm. When you attach an accessory they will specify a standard depth of 55mm. The job of the T-Mount is to attach the camera bayonet fitting to your accessory and provide the correct spacing of 55mm. 44mm accommodates the mirror flip up of a DSLR. Many T-Mounts, if not specified, are M42. T-Mounts can be also found for M48 or “wide” versions. Astronomy cameras have no need for the mirror box e.g. ZWO are often only 17.5mm. They usually are packaged with extension rings T-Adapters to maintain the 55mm standard and make them compatible. Without one/both of their adapters, filter wheels or OAGs can be included within the back focus required. I found the different sizes and names used a little confusing. This web link explains the different sizes: https://agenaastro.com/articles/guides/miscellaneous/astronomy-threads-explained.html M42 and M48 have differing internal diameters and the bigger size is less likely to vignette an image. M48 is also the thread size of 2” filters! Simon

How does a Vegemite lid manual control work? Probably very well (for the cost)? I heard a story that the BBC used to make football programs with the sound dubbed e.g. score a goal and they turn up the "canned" roar of the crowd to help the viewer listening at home on their valve radio - LOL. They found that their mixer desk was a bit too sensitive with small "twiddly" knobs and had them replaced with big round door knobs - the size of your fist and/or arm. The increased control e.g. move the small one a fraction of an inch vs move the big one also by the same fraction of an inch, gave great control and almost like having a 10:1 reduction. Is that the idea behind the Vegemite lid manual control? Simon

Andy, I know you moved from ZWO OAG and 290 to Celestron OAG and 174. I'm really glad it works for you. The 174 gives extra height so that you may get a better view of the back of the Reducer. Not sure if it still works when you have the guide camera horizontal and not vertical - that's how most users want to align their cameras. I have only tried Celestron OAG and 178. The first COAG was faulty and was returned. The second COAG has a ring below the helical focuser (NB it's not on the COAG you have). It may fix the rotation problem but it also puts the prism too far off centre. That's why in the scenarios (a) - (d) the results vary so much. When Celestron Support say it's not compatible, I simply returned it for a refund. I have kept the Reducer and also the 178 and obviously the EdgeHD 800. There are a couple of other scenarios I also need: Using a Baader ClickLock to mount a diagonal or an imaging setup for ease of switchover (needs a "thin" OAG); Using Reducer + OAG + DSLR - where COAG only gives BF of 121mm minimum (and I want to use 105mm); Using a Corrector/Reducer with a Refractor - the minimum BF is often 60-65mm and requires a "thin" OAG. Using Reducer (and without the Reducer) + OAG, keeping the parfocus of the guide/imaging camera unchanged; Using the guide camera horizontal and also vertical relative to the main camera (needs to be close to main camera); I already have a 178 guide camera and not the larger 174. (1) doesn't work with the thick COAG main body. (2) this doesn't work so using a bigger sensor on DSLR is not an option. (3) doesn't work with Refractors that have Corrector/Reducers and a minimal BF. Also not with filter wheels e.g. mono. (4) varying the spacing in front of the OAG allows removal of the Reducer , keeping the focus of the two cameras relatively unchanged. (5) want to be able to use the guide camera vertically and also horizontally and for the spacing to the main camera to be less than the minimum that's available. (6) 178 is what I already have to use as a guide camera. The 290 is probably the most sensitive guide camera available but also has a small sensor so searching for guide stars isn't easy with these, 178 is bigger and 174 is the biggest available. The Celestron Support "solution" is to vary the position of the prism using additional parts. The effect is to give more options to vary the BF in front of the OAG when using a Reducer. It's also the "solution" if you want to use a DSLR with the Reducer. Most things can be "fixed" e.g. one "simple solution" is to use a 1/2" SCT extender between the Reducer and the COAG - the space can be taken away behind the COAG to maintain the BF. This allows the two sensors to be placed closer. For a DSLR, another "simple solution" is to use a very thin (4mm) SCT adapter e..g a Baader one, so that the BF for a DSLR with the Reducer can be set at 105mm. There isn't an easy solution for using a Refractor apart from using a guide scope, but this increases the demands on the mount e.g. a bigger mount may be required. Having a FL of 2032mm, 1490mm, 700mm, 400mm etc. is the same as varying the EP for visual. To frame different targets requires a combination of SCT, SCT with Reducer, Refractor, smaller Refractor etc. Most Refractors provide a faster/flatter field with a Reducer/Corrector but the BF for these is often quite minimal - that's why other "thin" OAG are often used. The ideal is one rig that doesn't put too much strain on the mount and can be used interchangeably with every scope/reducer combination. Simon

I only have a problem using the Reducer with the COAG. The setup is the "normal" COAG one as shown in the manual (COAG instructions don't have a Reducer example) or with the Reducer (neither instructions references the other product), as you would expect: a. EdgeHD 800 - COAG - T adapters - ASI294MC, with QHY5III-178M in helical focuser (this is OK for both cameras); b. EdgeHD 800 - Reducer - COAG - T adapters - ASI294MC, with QHY5III-178M in helical focuser (this is NOT OK for the guide camera but is OK for the imaging camera); There is also without the COAG e.g. for "normal" use with/without the Reducer and one camera: c. EdgeHD - visual back - camera (QHY5III-178M or ASI294MC) (this is OK for both camera); d. EdgeHD - Reducer - T adapters - camera (QHY5III-178M or ASI294MC) (this is OK for both camera);. Where: COAG is SCT Adapter - Adapter 4.5mm - OAG - Adapter 12.5mm (as supplied); T adapters or visual back are to make up the BF of 105mm or 133.5mm - a combination of 11.55mm + 21mm + 16.5mm (as required); Cameras are ASI294MC (imaging) and QHY5III-178M (guide camera). So from the above, "without the Reducer": means (a), (c) or (d) and "with Reducer" means only (b). In the above, Celestron Support say that the COAG is designed for (a) but not (b). I think they mean originally for C8 but now (coincidently) also for EdgeHD 800. Of course, the scenario I really want to get working is (b) e.g. using EdgeHD 800 with Celestron 0.7x Reducer and COAG, with both cameras active. "OK" means the image is OK e.g. look at branches on a tree etc. and recognise them. "Not OK" means it's all washed out and very poor. It's not hard to see why the image is so poor when seen through the prism with the reducer - the prism is so high up that it's out of the field of anything decent to see. Simon

Glad to know that you have a working solution. The problem was when not using the Reducer (which I didn't have when I tried it). Without the Reducer the gap between the OAG and the back of the OTA is minimal, so with the thumbscrews pointing towards the scope, they caught on the focuser and focus locks. How close can you get the prism to the 294 e.g. centre of the prism to the centre line of the OAG? Your OAG is perhaps a little different e.g. there isn't a ring under the helical focuser - I could rotate the lock and this would limit the rotation of the focuser - so the thumbscrews were out of the way. However, if it fixes the thumbscrew problem, then it may have introduced another one. The minimum height I could lower the prism was to a centre line of 17mm and the view of the Reducer (when it arrived) was not very good. If you remove the guide camera and look in, do you see the image circle or only a small portion of it e.g. is your prism perhaps further in than I could achieve? One effect I noticed is that the 294 gives a very nice image but the guide camera is all washed out e.g. it struggles to see anything clearly. When not used with the OAG it's absolutely fine, so it must be how it's positioned? Simon

I want to put my steel tube tripod on something more permanent in the garden. I'm not sure of the mechanics for what makes for a more solid base than a 6" thick block of concrete with a diameter (if round) or square cast in my back garden. Not so big that I constantly step on it and firmer than a patio? Do I need to lay it (cast it) on bed of sand or gravel or use a membrane? Thanks Simon

Is that 100% true e.g. any scope that's F/7 or F/10 etc. has the same speed? So a 8" SCT with a Reducer at F/7 is more/equal sensitive as some 50mm guide scopes at F/7-ish? I must admit I thought an OAG on a SCT would have no trouble compared to a small finder (with it's tiny comparative objective area) - but maybe I didn't think it through enough. Simon

Hi Andy (and Knobby too) How are you finding the Celestron EdgeHD 800 + Celestron 0.7x Reducer and Celestron OAG "combination" for AP? I read through more of the topic - you switched from ZWO to COAG and small camera to 174 too. With it working, what height did you set the prism? I bought an EdgeHD 800 because it has a flat and crisp image out to the edges (according to the published "blurb") so ideal for AP as well as visual use. I also wanted a Reducer because the accepted wisdom here and on Cloudy Nights (CN) is that imaging with a longer focal length and slower F/10 makes the task particularly difficult. I also bought (but returned) two Celestron OAG whilst waiting for a Celestron Reducer to become available. Simon

You might try calculating the ratios of focal length and resolution. There is a formula for it. Or you could put the details into a calculator and compare the arc seconds result for the scope and the guide scope: https://astronomy.tools/calculators/ccd With an OAG, your focal lengths are equal and there are no flexure issues. So you only have to compare the resolution (pixels) of the two cameras and the answer is usually about 1:1. A good result for guiding with a camera is supposed to be 1:3 or 1:5 but 1:1 is even better. The size of aperture e.g. a 50m or 60mm scope should make a difference but probably won't e.g. use what you have. Having a slightly longer scope can improve things but 200mm vs 240mm isn't going to make too much of a difference. The problems start when you do the calculations and then expect a 1:10 difference to also work - but it might (just) be OK. Off-topic, sorry. I'm looking to use an OAG with an EdgeHD 800 and a 0.7x Reducer - but finding an OAG that will work is proving difficult. I haven't quite given up on the idea of using a guide camera and a scope e.g. a S/H ED 80 or a cheap achromat - what would work best? Simon

Do vibration pads do anything special e.g. dampen down vibration? Or is a solid base better to stand a tripod on? Simon

The ST 150 is a bit of a bargain. There is also a 150 SW at 10x the price. For the latter, FLO have an offer to save £50 if you buy the reducer at the same time. For that price you might expect them to include it! You are trading different things. The Newtonian has no glass, so avoids any chromatic aberration, that the more expensive refractor seeks to avoid. The ST 150 avoids collimating issues that Newtonian are known for. All Newtonian scopes (which includes the ones with a parabolic mirror) suffer from coma, so crow’s feet at the outer edges, which can be corrected. A Newtonian can have spiral canes which introduces four points around bright stars, which can be eliminated with curved vanes. There are practical issues with the Newtonian e.g. have to rotate the scope in the cradles to get a good viewing angle and you may want a short mount or a “booster” seat to be comfortable. Some Newtonian are big for their size e.g. some bigger ones are in smaller or shorter tubes and be less susceptible to wind etc. A camera may not reach focus on a Newtonian, otherwise the EP would be too far out for normal use. A refractor may require a pier to get sufficient clearance on a Eq. mount. Overall the best image is the one you prefer, with lots of other things to take into account. Simon

If you are worried about the age then ask the owner for details e.g. ask politely if they have a sales receipt and is there a picture of the serial number (grey sticker) on the OTA body. If they can't or don't want to tell you the history then you perhaps need to look elsewhere. The C8 has an open tube at the back so air can circulate (I have an EdgeHD 800 that's sealed, up to a point, with vents and a closed tube e.g. extra glass compared to the C8). So you really went to inspect the product before purchase and at the very least get lots of photos showing the condition and especially the optics. That's not to say that you can't get it cleaned inside/out. Discontinued can mean that the original package is no longer sold e.g. mount + OTA as a "discontinued" package. If you are not buying it with a mount then what it came with doesn't matter if it's not included. It's not from a "current" 8 SE because the tube is now orange, however this is a recent "marketing" thing as Celestron is trading on their heritage. Some folks worry also that their C8 is from a batch made in USA or is made in China. The most recent ones are made in China and this is actually a good thing because the quality and variability has improved no end and perhaps by also lowering (or keeping the price down) it has opened up the market to many more would be astronomers. Slightly off topic, the parent company of Celestron and Sky-Watcher is the same, it's Syntra, who also sell through the Orion brand in the US. The products are however distinct e.g. A SkyWatcher mount is almost identical to an Orion one (may be black vs white) but is different to Celestron one. A Celestron HC is using different software to Sky-Watcher etc. As an example, if you are interested in reading about or knowing what the HC for the HEQ5 Pro is like, then you have to go to the US Orion website to download the V5 manual as the European SkyWatcher website only goes up to V4 (the answer is that it has the shape of the V3 HC, with the buttons and layout of V4 but with the USB interface that comes with V5 and it has a 40K object database not 13K (there is also RS232). In this respect the US is perhaps ahead of the UK. The included manuals are up to date in the box. Things like mounts also go through product changes as well, so the HEQ5 Pro gets an illuminated polar scope and more recently a variable brightness through the HC. The manual is for the mount without a HC, so is a bit "generic" and there is an updated polar screen (wha you see) that they call 2012-2030 - it doesn't show Cassiopeia (which you couldn't see in the polar scope anyway). There's a separate manual for the HC which covers the mount "electronics" too. Celestron avoid the polar scope altogether because it's not included with their mounts - you can buy it as an extra if you want one. Bad polar alignment with clever electronics does not make it into good polar alignment, which is a prerequisite for good results. Wifi is another example of updates, there are at least three version of the WifI plugin module (also used a a component inside the Evolution) and the results range from poor to about OK. For this reason my experienced users will recommend having a wired connection. Having USB with a laptop connection is an obvious example of where the market for mounts didn't innovate quick enough. I do like having an App e.g. having a planetarium program on a phone (better on a tablet) is really handy and compared to having a laptop the ergonomics are much better IMHO. I don't find it a problem to transfer an NGC number into the HC to slew to a target a problem and I can put the iPad down/way and not rely on it. HC buttons are better than tapping on a screen IMHO too. Simon