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Yes, for dark optimization to work - you need to have proper bias, and CMOS sensors don't have proper bias, so it's best to avoid dark optimization as it will cause issues - like you've shown.

Could be many reasons, but let's list a few: 1. changing seeing conditions between OIII, Ha/SII - you could analyze this maybe by examining what time of the night did you do each set, was it on same or successive nights and what was guiding like for each session. If OIII was first or last in single night - it is more likely that seeing had something to do with it, if it is in the middle of the night - it is still possible but less likely. If each was taken on a separate night - highly likely that it was the seeing. Poorer guide RMS often means that it was either the seeing or maybe wind? 2. Different signal levels will cause different level of "auto stretch" / "auto develop". If you want to see if stars are similar in size (or different), you should check actual FWHM of respective stars to see change in "bloat". 3. It might be that optics + flattener is better corrected in green than it is in red. I doubt that you would see this from scope alone, but with flattener - it might be an issue. 4. In principle it could also be due to filters, but I don't think Baader filters are to blame here. Many people use them and no one (including me) reported this. In general it is other way around - Ha/SII tends to be sharper than OIII because longer wavelengths are less impacted by seeing than shorter ones.

Maybe simplest way to try it is - to try it Read voltage from your mains adapter, and see how much amperage it is supposed to give (mine is something like 19.5V and 4.8A). You don't need as much amperage - can be a bit less, because these mains adapters are designed to both power laptop in work and charge at the same time - hopefully it won't do charging of the battery, just powering laptop. See if your step up converter can deliver enough power and set it to proper voltage that you read off mains adapter. Do be very careful about plug polarity - measure it on your current mains adapter. Get another plug like that and make a lead with it from step up (of course, again minding correct polarity). Then plug laptop into battery instead of mains and see if it will work. You can do it via 12V DC - > 240V AC and then use regular adapter. This way it will try to recharge your battery when it drops, so maybe remove laptop battery, or tell laptop in power management not to recharge battery (I don't even know if there is option for that) Total losses are unlikely to be better than something like 15% and can be as bad as 40% - depends on efficiency of converters. But let's use 20% losses. Mind you that using step up and doing 12V -> ~18V (or what ever lap top needs) will have similar performance, but might be smaller in size and easier for DIY. Laptop won't draw max current all the time, but it will certainly need something like 35-40W in normal working mode (no heavy processing or such). This in turn means about 50W load on battery, and at 12V it is about 4A. 4A from 75Ah battery in principle should be able to power laptop alone for about a 18h.. On the other hand, we can look at it like this: - mount power - 2A? - camera cooling - 2A? - laptop - 4A? - gadgets (flat panel, motor focuser, .... anything that uses just a bit of power - and not continuously) - this we won't count as others won't have continuous draw at max rating so there will be plenty of power to spare for these devices So we have something like 8A of draw (although not continuously). We want to be able to run 8hours in the field (should be enough for complete session together with setup and everything) - that is total of 64Ah - anything above 70Ah should be enough (providing it is deep cycle).

At the moment - just mains power Still don't have portable rig. However, I've found that for Dell laptops, if you provide needed voltage and current on adapter plug - it will work but will not charge (which is good - don't need to drain current from main battery to recharge laptop). I've found very cheap step up/step down DC/DC transformer - just need to try it out. It provides around 3A of current (my current charger is something like 4.8A - but it needs more power in order to charge laptop). I'm fairly confident that laptop will run on 19.5V / 3A (that is almost 60W of power - should be enough for just running computer). And need 7.4mm laptop power plug - don't want to cut into laptop mains adapter that I already have.

Here is some info on this barlow: - focal length of this barlow is 62.9mm - for magnification factor of x2.7 you need to place it 105mm "from the center of the last lens", or another way to put it - from "highest" point on the surface of the last lens (that being the center of lens of course). You can actually calculate required distance by using barlow formula: Magnification = 1 + D/F Where D is distance from the lens and F is focal length of the lens. If you plug in the numbers - you can work out distance from the "center" of the lens assembly (principal point)- not to be confused with center of last lens - it is "middle" of the lens assembly rather than point on surface of the lens. 2.7 = 1+D/F => 1.7 = D/F => D = 1.7*F 1.7 * 62.9 = 106.93mm This agrees well, so principal point to focal point is 106.93mm - that puts principal point about 1.93mm "inside" last lens. Anyway - here you have it. It should be about 104.1mm from shoulder because it is about 1.1mm "in front of the last lens". If you place your sensor further or closer - you will get different magnification - handy for adjusting sampling rate, however nothing to do with sensor size.

Wondered the same myself for my dell laptop. Ideally I'd like something like a car charger but without charging capability - just powering laptop after battery is low. Issue with dell is that it won't boot if charger is not "genuine" (there is some sort of identification protocol between laptop and charger). Another option that I considered is "dummy" battery - just empty battery slot without actual battery inside - connection to external power tank and appropriate voltage, but then again - battery is sort of "smart" battery - it reports level of charge and what not and I don't think simple connection to proper voltage will work.

For smaller sensors you don't need flattener. You might want one for APS-C sized sensor (I'm not sure). RCs have rather flat field, but not fully flat - for large sensors they need flattener. I use RC8" with ASI1600 without flattener and field is good on that size (21mm or so diagonal). This scope has 1370mm FL and with 460ex this will give you 0.68"/px - and that is rather high sampling rate and you will be oversampling natively. There are two things that you can do - add FF/FR, or bin. I think that you should bin x2 - that will give you 1.37"/px - and that should be rather good for HEQ5 and regular guiding results (something like 0.8" RMS). When you bin x2 it's like having twice shorter focal length so you will effectively have "F/4.5" scope - which will be fast enough (F/ratio and "speed" of scope is not measure of how fast you will take images - it's aperture at resolution, and in this case you will be using 6" at 1.37"/px - which will be quite fast). Here is an example for you - this is two hours of lum in rather heavy LP (mag 18.5 skies) - 8" scope (F/8 natively - also RC but 8") at ~1"/px: I would not call that slow ... You can "speed up your scope" with use of FF/FR, and a good one would be Riccardi x0.75 FF/FR - but that would give you 0.91"/px - and I think you will still oversample on this resolution. Binning with FF/FR will give you 1.82"/px - and that is going to be rather low resolution - comparable with 80ED - so you will gain nothing (apart from speed, because of almost x4 light gathering for same sampling rate).

Maybe this: https://www.rothervalleyoptics.co.uk/altair-astro-6-f9-ritchey-chretien-astrograph-telescope.html

Ah sorry I thought you were asking about IR pass filter (did not read what you've written properly). No, IR cut will not be much of a use for guiding. Even if stars are a bit bloated it does not matter for guiding. Anyway, you can use one of those adapters if you still want to try some sort of filtering on your guide scope (either IR/UV cut or IR pass filter).

In principle it might. Longer the wavelength of light - less bending there is, so in IR you should be affected by seeing the least. You will loose some of camera sensitivity, but that should not be an issue with longer guide exposures. You don't need any special T2 size filter - regular 1.25" filter is enough, you only need an adapter like this: https://www.firstlightoptics.com/zwo-filters/zwo-t2-to-125-filter-holder.html In fact, you might have received one with your camera already (I know I did for one of my ZWO cameras).

Depends on a cam. I did some 60s exposures with ASI185 and it worked to some extent. I don't remember going longer than that.

Yes, there is residual amp glow. Could you upload this light and set of darks that you used to calibrate it for inspection? There might be something that is causing this that could be solved?

Fancy an open cluster? M29 is nicely positioned and quite compact - framed nicely in your FOV. Globular - M15. Nebula - Maybe Crescent nebula? It is nicely framed. Cocoon is also good fit Galaxy - NGC7331 is always a nice target.

I did read once a review of this unit, and author did get tighter stars by using it, but can't remember what mount it was on. Will try to find it again and post a link Yes, you are right that some mounts are rather expensive, but why consider GM2000 and not something like Mesu 200? EQ8 + AO device will place you in Mesu 200 price range, and I have sneaky suspicion that Mesu 200 will deliver at least as good performance if not better without complexity of running an AO unit.

In my view - completely useless thing. It won't correct for seeing for different reasons: - it only corrects for first order aberration - tilt - seeing aberrations, or specifically tilt is very local phenomena - seeing happens in higher in atmosphere at at least couple of kilometers of altitude. It is enough to move couple of arc seconds away from a guide star and that translates to significant length at that distance (for example 20 arc seconds at 5km is already about half a meter - seeing cells tend to be less than that). Any sort of wider field will be distorted by different amount of tilt - you can easily see this effect if you look at planetary recording or maybe Lunar recording - distortions (jumping around of the features - mostly due to tilt) is different at different places. Correcting for tilt at location of guide star will do nothing for rest of the image and probably cause more harm then help. - it does corrections on time scales that are most of the time above time scales of seeing changes. It does something like 30hz max if I'm not mistaken, and seeing often goes as fast as 100hz or more. It does have one use, and it is at best limited at that - correcting for a rough mount. If you want good guide performance but your mount is rough and it has small time scale error large enough (like 0.5"-1.0" or similar jitter) that can't be corrected with guiding because guide exposure is longer and mount is not as responsive enough - this will catch it and react provided that seeing is good enough that any guide star deviation from true position is due to mount and roughness rather than being "masked" by seeing. On the other hand - why buy such expensive unit that might not perform as expected when you can instead sell current mount + invest that money into purchasing a new better mount that will be smoother and guide better.

Don't use bias in regular workflow - you don't need them and they can cause issues (maybe even issues that you are seeing). Since you did not take flat darks (or dark flats - whichever way you prefer) - use bias that you captured instead of those. Btw offset of only 15 looks suspiciously low. Since you have bias subs - you can check if offset 15 is indeed adequate. Could you do following: Make a stack of bias subs only but use simple minimum stacking method, then run stats on it (min,max, average, stddev and such) and histogram and post those?

I don't know any company that does such a thing, but why not enlist help of fellow SGL members? Many people enjoy processing data, and all you should do is create a post with a link to your data and ask people to process it - I'm sure you'll get many different renditions of your target and you can select one to your liking.

Yes, and it works well. I've done it on short & fast ST102 F/5. I made couple of aperture masks, and did some testing. Even managed to take a decent deep sky photo without any blue bloat around stars - by using 66mm aperture mask and yellow #8 filter. Just be aware that putting aperture mask on will reduce maximal attainable magnification - good rule as always is aperture in mm x2. 80mm scope will be good for up to x160. Of course image will be dimmer. Btw, I've now got Evostar 102 F/10 and Baader contrast booster filter removes almost all CA while keeping things almost natural looking (there is small color shift). If you go for something like 70-75mm aperture mask, you will in principle eliminate chromatic aberration pretty much completely (CA index >5). Btw, here is "a study" for photographic purposes I did at a time with ST102: Rows contain same image, but stretched to different level (first one the most obviously as hot pixels / noise start to show). From top to bottom - no mask, no mask+#8, 80mm, 80mm+#8, 66mm, 66mm+#8, 50mm, 50mm+#8. Exposure times were scaled appropriately.

Just to throw in a wrench or two ... Since OP almost decided to go for Mak180, I'm wondering if this could be something worth considering: https://www.teleskop-express.de/shop/product_info.php/info/p10753_TS-Optics-8--f-12-Cassegrain-telescope-203-2436-mm-OTA.html As far as I know, Australia has a dealer of GSO equipment as well, so worth checking there for availability as it would certainly be more affordable then shipping it half way across the globe. Quick comparison: 200mm vs 180mm - more resolution and sharper image at lower magnifications (given same optical quality). Price about the same - slight edge for 8" Cass in TS pricing. Slight weight advantage for 8" Cass (7.5 vs 7.8kg). Much less of a dew magnet since no front corrector plate. Cool down time is consequently less in 8" Cass Probably better focuser as it has 10:1 reduction and does not cause mirror shift when focusing. CO size - Mak180 probably wins - I've seen figures around 30% quoted online - 33% for 8" Cass F/ratio and focal length - again +Mak180 as it is F/15 vs F/12 and 300mm additional FL - easier on EPs, easier to reach high magnifications. 8" Cass - diffraction spikes - might detract some people, better baffling of the tube - probably very small boost in contrast because of this.

Don't get AZ3 - I had that exact combo and later switched to AZ4 on steel legs. Very big improvement. AZ3 has couple issues that annoyed me quite a bit. Stiff to move telescope by hand (although there are adjusters - it is not very smooth mount). Slow motion controls needed rewinding after a bit of use - they are not 360 degrees but rather section of the circle so you when you reach the end - you need to move scope manually and "unwind" slow motion control back to middle (if you plan to pan around slowly) or all the way if it is only for tracking single object. Looking at zenith was next to impossible on that mount. If you want slow motion controls then AZ5 is better option than AZ4. With AZ4 it is pretty much only feature that is missing (and I believe AZ5 is slightly lighter).

Not very long I'm afraid. Two major things that you will be facing is periodic error and polar alignment error. Out of the two, I think that periodic error is going to give you more issues than polar alignment error. Let's run some numbers so you can get the idea of what sort of exposures will be attainable. You are imaging at ~ 1.6"/px, so let's set upper limit to 2px, or about 3" as maximum drift per exposure that will produce acceptable stars (a bit elongated, but still round enough). With regular polar alignment, you are looking at something order of 5 minutes of arc or PA error. In worst case scenario this translates to drift of about 1.3"/minute. Stock HEQ5 can have as much as 30-40" P2P periodic error. Since you've done belt mod, this tends to drop quite a bit, but it is still in range of let's say 12-14" P2P. Period of HEQ5 mount is 638s. If we assume perfect sine wave then max RA drift rate due to PE will be 4.13"/minute - in reality PE is never sine wave and you can expect it to have a bit higher drift rate at some point, but let's go with 4"/minute because P2P might be even less like 7-8". This shows that PE will be limiting factor, rather than PA error (unless you did a very poor job of polar alignment and error is something like 16 minutes of arc - which is quarter of a degree, so yes very large indeed). With drift rate of about 4"/minute you are looking at about 45s exposures. This is worst estimate, so not all frames will be distorted (it depends where on period of mount you are at the moment, what is the DEC of the target, etc ...). I think that you can use 1 minute exposures and expect to throw away something like 10% of frames if your target is close to equator. Higher up in DEC you can maybe do 90 seconds and still keep most of your subs.

Well spotted - I did not see it is in fact different mount. I guess freedom find is indeed handy - you can point the scope by hand and it will know where it is pointing and continue tracking. It sort of defeats the point in getting this package - resale value won't be as good as full Gti version.

Well, I was thinking about mentioning that scope, but decided not to because you mentioned previously that: As far as AZ-EQ avant goes, I have no idea how good it is. I like the idea of such mount, and I think that it is probably one of better light weight grab & go beginner mounts. It looks versatile, and only down side that I can see is fairly small capacity of only 3kg. Then again, one can't expect grab and go small mount to handle 10kg of load Here is fairly nice review video of this mount: https://www.youtube.com/watch?v=wkVergOxt_E&t=706s I already fast forwarded the video to important part (102mm Mak and AZ-EQ avant section as video overviews whole avant range, but you have "jump list" in description to go to particular segment of review). Here is quick list of differences between Mak102 and small refractor that you need to be aware of before deciding: - Mak will have significantly higher magnification and smaller FOV with same eyepiece because it has about twice focal length of refractors (more than twice compared to 705 and just a bit less than 707). It can give you about 1.2-1.3 degrees field of view with 32mm eyepiece - still wide enough for general observing, but it simply can't provide you with wide field of view - like 2-3 degrees that is possible with short focal length refractor (or reflector). You can use tool that I linked previously to see field of view with different eyepieces. - It is better suited for viewing Moon, planets and double stars than those small refractors - It won't have any chromatic aberration and will give sharper image - there will be a bit of "cool down" time when you want to use it at higher magnifications - about 10-20 minutes or so for image to stabilize. There is front glass element and main mirror in this scope design - larger pieces of glass need more time to come to ambient temperature. This is more pronounced in winter if you keep your scope at room temperature (like in house / apartment) and take them out to observe. - you can still use it for terrestrial observations - with 90 degrees astronomical diagonal it will have left/right reversed so you need amici prism to get proper image orientation. However it will give you quite a bit magnification - about x4 or more over standard binoculars (depending on eyepieces used) - there is a very small chance that you will have to collimate it. It is very slim chance, as these scopes hold collimation very well and are sold already collimated, but unlike small refractors (that can also get out of collimation, although similarly unlikely) there is a way to collimate it yourself. Small cheap refractors usually have lens cell that won't allow for collimation - lens are fixed in place at factory. With Mak you can adjust primary mirror, but it is hardly unlikely that you will have to do it - it will come in good collimation and stay that way for years. In fact - there is a section in user manual that describes this: https://smallscopefocus.files.wordpress.com/2016/06/makcasscollim1.pdf and to quote it: This is from Orion's manual - but those are same scopes under different brand.

Old saying goes: "Best scope is the one you use most often", so you are right in saying that you don't want something that is going to end up collecting dust because it is too complicated/heavy to use regularly, or does not provide enough enjoyment. There will be no difference in 705 vs 707 with regards of what they can show you on deep sky objects. 707 will have slightly narrower field of view when using same eyepieces, but 700mm focal length is not very large focal length, in fact as far as visual goes it is shorter focal length. I use visual scopes that have 1 meter of more of focal length and never felt "boxed in" with "small" field of view. There are just a few objects out there that can't fit in such FOV - Andromeda galaxy and couple of large nebulae (North American nebula for example) which are couple of degrees in diameter. If you want to compare the two scopes on FOV that you will have with 25mm stock eyepiece - visit this page: https://astronomy.tools/calculators/field_of_view/ For example, here is comparison of two scopes on Orion Nebula (something that you will definitively enjoy observing - although probably won't be able to see as much of it with 70mm aperture, unless you have very dark skies). A side note, I've seen Mercury 705 come with AZ3 mount. I had that mount and was not particularly happy with it - sold it. It was stable enough, but my primary objections were - It has to be rewound every so often to be able to use slow motion controls. It's not very smooth - at least mine was not, and it is very hard to observe near zenith - and that is the place you most often want to observe deep sky objects as there is least of atmosphere and light pollution is often of the least intensity. I've found a very interesting package that you might want to have a look at: https://www.firstlightoptics.com/sky-watcher-az-gti-wifi/sky-watcher-mercury-707-az-gte.html Some people prefer manual scopes to start with, some like go-to ability. For planets and double stars it would be good to have tracking. But this is not main reason I'm telling you to take a look at that package. In the case you decide that observing is not quite your thing, I'm fairly certain that you will sell more easily AzGti mount than any of the starter mounts. Unfortunately az-eq avant mount is not sold with Mercury line of scopes, neither as stand alone mount, although I feel it would be probably best starter mount for such scope - it can work in both EQ and AZ mode, and can be easily fitted with tracking motor (and rather affordable one - it's like 50 euros or so).

What is your budget btw? Maybe check out this little guy instead? https://www.firstlightoptics.com/evostar/sky-watcher-mercury-707-az-telescope.html It is F/10 version of 70mm SW scope