johnturley

1 hour ago, Louis D said:

You don't say which coma corrector you were using with your f/5 Newtonian.  I've found my 30mm APM UFF to be sharp to the edge with a GSO CC in my f/6 Dob.

I've measured its AFOV to be 73 degrees.  It's eAFOV (to plug into TFOV calculators) is indeed 70 degrees due to slight distortion.

I don't usually use a coma corrector with my f5 Newtonian, although I do have an Explore Scientific HR Coma Corrector, no doubt the results would be better if I used it, as I tried once with my Baader 36 mm Hyperion Aspheric, and it gave improved results. I don't usually use the coma corrector as its fiddly to use, and the weight of it causes balance issues with my fork mounted Newtonian. The whole point of getting the StellaLyra 30 mm UFF, was to get a well corrected eyepiece which doesn't require a coma corrector, I'm really surprised that you find that there is significant coma with your 30mm APM UFF at f6. 

Interesting that you find the APFOV to slightly greater than the stated 70 degrees, which is unusual, with most eyepieces the APFOV tends to be less than what is claimed.

John 

Ordered a StellaLyra 30mm UFF from FLO last week, and it arrived by express courier the next day, and since than have been able to try it out a couple times through my 14 in Newtonian, and overall quite impressed. As mentioned in another thread, I have been looking for some time for a low power wide field eyepiece that is both not excessively bulky and heavy, and will be sharp to the edges of the field of view in an f5 instrument, and the StellaLyra 30 mm UFF comes close to achieving both these aims. At 550g (not including lens caps, 570g with) it is no lightweight, but this is about 2/3rds of that of my ES 24 mm 82 degree eyepiece or 35mm Panoptic, and about half that of a 31mm Nagler, or a 30 mm ES 82 degree.

Although the star images at the edge of the field of view through my f5 Newtonian were by no means perfect, they were noticeably superior to those in my ES 24 mm 82 degree eyepiece, and vastly superior to my 36 mm Baader Hyperion Aspheric. Although in the case of the former I was comparing an APFOV about 15% smaller, one thing I liked about the StellaLyra was that it had a sharply defined edge compared to the rather mushy edge of the ES 82 degree, and the whole of the field of view was immediately visible, as opposed to having to move the eye around in the case of the latter. 

If anything the claimed 70 degree APFOV of the StellaLyra was a bit on the modest side, holding the two eyepieces side by side, the APFOV was noticeably larger than that of my 24mm 68 degree Panoptic, similar to that of my 36mm 72 degree Hyperion Aspheric, and very close to that of my 17.5 mm 76 degree Morpheus. Before purchasing I was a bit worried that the actual APFOV might be significantly smaller that that claimed, as was the case with a StellaLyra 50mm Superview eyepiece that I once owned, which originally claimed to have an APFOV of 60 degrees, but turned out to be only around 45 degrees. With hindsight, I don't think that it is actually possible to produce a 50mm eyepiece with a 60 degree (or greater) APFOV in a 2in barrel.

Furthermore at £179 (from FLO) the 30 mm StellaLyra UFF, although not cheap and having a smaller APFOV, is quite modestly priced being just over half that of a 30 mm ES 82 degree, or 1/4 that of a 31 mm Nagler. 

John 

5 hours ago, Mikkel Kroman said:

Hi all

Will I need to use the field flattener if I use my 1600MM Pro? It does not have a full frame sensor so I would think no.

Kind regards

Mikkel

I thought that the whole point of the Petzval based FSQ series is that they have a built in field flattener, and that you don't need to use an additional one.

John 

If the mirror is about 10mm higher in the new cell than in the old one, then surely you would need about an extra 10mm of out travel on the focuser., which you can achieve with an extension tube if there is insufficient out travel on the focuser.

John 

Arrived yesterday from FLO, a 30 mm StellaLyra Ultra Flat Field eyepiece.

I have been looking for some time for a low power wide field eyepiece that is both not excessively bulky and heavy, and will be sharp to the edges of the field of view in an f5 instrument, and after reading good reports hope that this will fit the bill. At first glance it appears to have as advertised, a genuine 70 degree field of view, unlike the 50 mm SuperView eyepiece that I once owned, which originally claimed a 60 degree APFOV, but only turned out to be around 45 degrees. 

Although at 70 degrees the APFOV is some what smaller than that of a 31 mm Nagler or 30 mm ES 82, but at 570g, although no lightweight, this is less than half the weight of the others, and at £179, about 1/4 and 1/2 of the price respectively. I do have a 36 mm 72 degree Baader Hyperion Aspheric which is even lighter, but the edge performance, especially in my f5 Newtonian, is not that great. 

John 

On 05/10/2022 at 21:07, MetroiD said:

I recently had the opportunity to put these three side by side. Considering their TFOV is almost exactly the same, I was slightly surprised by my findings so I thought I'd share with you guys. 
tl;dr: The APM UFF 30mm is bloody amazing.

Meade's 24mm UWA was the very first widefield EP I purchased almost as soon as I'd laid eyes on this holy hand grenade of an eyepiece. And I did learn to love it - much more so in my bottom-heavy 12" flex tube dob than the smaller ones that preceded it - but I was always bothered by its ergonomics (which had admittedly attracted me in the first place). The widefield 24mm was in regular use as my lowest-magnification "seeker" eyepiece - but then earlier this year the EP itch saw me grab an APM UFF 30mm from Germany - which coincidentally was the direction in which the Meade later departed. But not before I'd had the opportunity to test these two side by side and confirm that the much newer design in APM's UFF series trumps Meade's variation on the Nagler.

Field curvature was present as a shift in focus in the outer ~10% of the field in the Meade even when simply looking at star fields. With a clear target in sight, things did seem a tad better, no doubt due to the UWA's rather engaging 'spacewalk' view. However, when the same object was seen through the 30mm UFF, things immediately looked much crisper and yes, even more 'exciting'. I know that the latter is a poor marker for any eyepiece's performance but it's still part and parcel of the whole starry skies experience. Colour transmission in the APM was decidedly more neutral and contrast was on a different scale altogether - apart from the fact that the field was... well, ultra flat - there's a reason they called it that. Regardless whether I was looking at random star fields, larger targets (think M31), clusters, nebulae or the moon, the results remained unchanged. Better design, better optics and definitely better coatings - the APM won hands down. 

Shortly after the 30mm UFF had carved itself a firm place in my EP case, I stumbled upon a 100-degree Skywatcher Myriad 20mm. Buoyed by the fact that my flex-tube telescope had already proven it had a way with heavy eyepieces, I jumped at the opportunity - especially seeing as I'd been casting glances at the rebranded APM XWAs for a while.

By the time I could take my two lowest-magnification eyepieces out for a spin, the Hercules Cluster was high enough to provide a wonderful arena for the battle between the UFF and XWA's ancestor-of-sorts. Considering how it cost almost twice as much as the UFF (both used), I was looking forward to amazing feats from the Myriad. I aimed my f/4.9 reflector at the Hercules cluster and was half-expecting something along the lines of an Obsession Telescopes ad. In went the 600-gram EP - but my jaw remained very much undropped. I had already peered through a 21mm Ethos at that point so I knew what 100 degrees looks and feels like but on this occasion, I was immediately transported to the feeling that my old 24mm Meade used to give me. Very nice indeed - but still a performance that could be upgraded upon. The UFF readily revealed a much more crisp layout within M13, and I felt as though I was even seeing more stars within the globular cluster. By the time my eyes had gotten used to the improving conditions, I was already convinced that the lightweight UFF was the one to keep. I tried a quick glimpse at low-lying M31 - not a good view by a long shot so neither eyepiece seemed to perform particularly well. Clearly though, the UFF showed better transmission. 9 elements in 6 groups for the Myriad vs 9 elements in 5 groups for the UFF - apparently, it does make a difference in terms of transmission so it would be interesting to see actual values on this. 

Curious to find out whether there was any discernible field distortion with either, I then started randomly starhopping and taking in the widefield views. I still wanted to be amazed by the Myriad but kept confirming that, in this telescope, the UFF was simply superior. In the end, the Skywatcher/OVL EP didn't drop my jaw - but it definitely made my head spin quite a bit. That night I'd driven about 40 minutes away from home to enjoy better viewing conditions- but by the time I decided to call it a night, I was so nauseated by all the starhopping that it took me about two hours before I could finally crawl into bed. Lesson learnt the hard way: "floating in space" is not all it's cracked up to be.

A few months later, I had the opportunity to test the Myriad vs the UFF once again, this time in a 14" f/4.3 Newtonian. As I'd expected, the field distortion I'd already sensed in the 20mm Skywatcher was far more discernible. But what sealed the deal for me was the view of M57. In the UFF, despite the very low magnification, the Ring Nebula almost showed some level of detail. The 20mm Myriad should have made for a much clearer view given its 50% increase in magnification vs the 30mm - but I just didn't feel like I was able to see any more detail than with the UFF. After this session, the Myriad found a new home - along with my 12" dob. The featherweight UFF's performance in the rather quick f/4.3 truss tube convinced me that I could get away with using my current EP collection without a Paracorr - so we quickly made friends with the 14" scope, and by the looks of it, my 30mm APM has cemented its place as my go-to widefield EP.

Overview
Conditions: Bortle 4>3 skies
Observer: no issues w/ vision, don't wear glasses
Telescope: 12"/305cm f/4.9 Newtonian; later 14"/350cm f/4.3 Newtonian
Focuser: Omegon Monorail Steel track 
Corrector / Barlow: None
Filter: None

Specs for each eyepiece based on 12" Newtonian parameters: 
Meade UWA 24mm: AFOV 82 / 78.7 arcmin; magnification 63x; exit pupil 4.9mm; eye relief 17mm; calculated field stop 34.3mm
Skywatcher Myriad 20mm: AFOV 100 / 80 arcmin; magnification 75x; exit pupil 4.1mm; eye relief 15mm; calculated field stop 34.9mm
APM UFF 30mm: AFOV 70 / 84 arcmin; magnification 50x; exit pupil 6.9mm; eye relief 22mm; calculated field stop 36.7mm

Meade UWA 24mm: 
+ Cheap(er than the other two)
+ Very engaging views
+ That big cloak really does its job well and helps find / retain the perfect eye relief
? Decloakable - you could slim it down if you're so inclined
- Very bulky and heavy
- Noticeable field curvature when compared to more modern designs
- Can get greasy: Meade have gone slightly overboard with the oil on the cloaking mechanism

Skywatcher Myriad 20mm:
+ Huge field of view
+ Great eye guard - I've always been a fan of twist-up rather than fold-up, especially with such big EPs
- The sheer size of it
- Some field curvature - nothing too dramatic considering the AFOV.
- Pricey and hard to find - long lead times when new, a rare Pokemon on the second-hand market

APM UFF 30mm:
+ Brilliant, sharp and engaging view
+ Light transmission and contrast on par with the best EP's I've ever used
+ Ergonomic: light and compact EP, great fit for truss-tube dobs
+ Quite affordable given its performance

Nice report, I'm seriously think of getting the 30mm StellaLyra variant (from FLO), and selling both my ES 24 mm 82 (which I understand is similar if not the same as the Meade 24 mm UWA), and Baader Aspheric 36 mm). The only thing putting me off is that I had for a short period a 50 mm StellaLyra eyepiece, which claimed an APFOV of 60 degrees, but in reality it was around only 45 degrees.

John 

Thought I would post some images of Mars, showing a similar area of the planet taken through different scopes, and different techniques to show the different image sizes obtained.

The first image is of Mars taken on 12-13/11/2022 through my Esprit 150 and ZWO ASI 462 Planetary Camera using a 2.5 x Powermate (effective focal length 2,650 mm) giving f17.5

The second image was taken about 30 minutes later through my 14in f5 Newtonian with the same setup (effective focal length 4,500 mm) giving f12.5.

The third image was taken in September 2020 (before I obtained my planetary camera) through my 14in f5 Newtonian, and Canon 6D digital SLR using eyepiece with a  9.7 mm Plossl eyepiece.

The images were processed using AutoStakkert and/or Registax with a bit of polishing in Lightroom

Note the superiority of the ZWO Planetary Camera over the digital SLR.

I am also a relative beginner to planetary imaging, and my results are nowhere near as good as those of Neil Philips or Geoff Lewis, I would have thought that with imakebeer's Skywatcher 150P it should be possible to get results nearly as good as those with the Esprit 150. 

1 hour ago, PeterC65 said:

This web page looks like a good summary on ADCs (it is referenced in the SharpCap manual). The with and without images show quite an improvement and the ADC seems to be beneficial for visual as well as camera observing. I do very quickly run out of in focus with the 150PDS but not so much with the 72mm APO. Next time I'm observing Jupiter I will check to see what atmospheric dispersion I am getting.

 

Interesting read, in particular it states that :-

'ADCs are designed to work best at high f-ratios. At short f-ratios or with large amounts of prism correction, aberrations can be introduced which can start to offset the overall benefits. To reduce aberrations on short focal ratio scopes it is best that they are placed directly after the Barlow lens and a reasonable distance from the camera. For longer f-ratio scopes, such as SCTs, putting the ADC before the Barlow is less problematic and has some advantages in increasing the available amount of correction for low altitude objects.

I've only tried using my ZWO ADC with my 14in Newtonian at its native focal ratio of f5, maybe I would get better results if I tried using it with a Barlow. There has been a lot of discussion on 'Cloudy Nights' with regard to to the very expensive (£3.5k) Gutekunst ADC's, and they are best used in conjunction with a Barlow.

However the ADC didn't seem to give much improvement with my f7 Esprit 150 either, which incidentally unlike my 14in Newtonian, doesn't usually exhibit much false colour due to atmospheric dispersion, unless the object being viewed is very low down, which is why I thought 'imakebeer' would not notice much improvement with his Skywatcher 150P. 

1 hour ago, PeterC65 said:

 

I don't have an ADC so can't comment on their usage or effectiveness.

 

 

I don't think that you would notice a massive improvement with an ADC especially on Mars with its current high altitude, and with a 150 mm scope. 

In addition with a Newtonian Reflector, you may not have sufficient in travel to add an ADC to the light path.

I do have a ZWO ADC but have never bothered using when it when imaging, I found last year when Jupiter was quite low down, it improved the visual view through my 14in Newtonian significantly, but not much difference this year.

John  

11 minutes ago, vlaiv said:

You can get equally decent image size by taking properly sampled image and just upscaling it - look at my post above.

I personally prefer smaller but sharper image than large blurry one.

Which program do you recommend for upscaling, I tried upscaling some images in GIMP, but the results were not that great. 

Also if the initial image is too small you may struggle to get a sufficient array of alignment points in programs such as AutoStakkert and Registax.

John 

20 minutes ago, HollyHound said:

I'd say that's an excellent move... you don't be disappointed for sure 😁

I'd also say, that I'm not sure I'd pay the current retail for the DZ over and above the DC/DF either, no matter how much I love mine 🤔

Enjoy it, have a great Christmas and hopefully some clear skies over the festive break 🤞

I had some thoughts of getting a 100 DZ as a potable instrument possibly to take on holidays to Tenerife, and possibly to the 2024 Mexico Total Solar Eclipse.

If there is no discernable difference in performance, maybe the cheaper DF (which I understand is also more readily available) would be a better option with its shorter tube length, which could make the difference regarding what you are allowed in cabin luggage. Takahashi claim that the 100 DZ on be easily carried on most commercial flights, but someone advised me that this is NOT in fact the case.

2 hours ago, geoflewis said:

Thanks Vlaiv, I know that you’ve said it many times, but my personal experience (and I think many others) says that oversampling gets better results. I have tried both correct sampling and over sampling and my oversampled images are almost always the better ones. I don’t understand why, maybe it easier to obtain accurate focus with larger over sampled image on screen, or something else, but operating at F21 or F24 gives me better results despite ‘correct’ sampling is ~F14. I cannot deny the maths/physics that you describe, but equally I cannot deny the evidence of my own eyes.

Depending on your system, you may also need to oversample and at a higher focal ratio than the theory suggests, to get a decent image size.

John 

Managed a brief session on Mars last night before it clouded over, conditions were rather unsteady with a breeze causing some movement of the telescope.

The image of Mars below was taken through my 14in Newtonian, ZWO ASI 462 Planetary Camera, 2.5x Powermate giving f12.5, 2 minute exposure, Capture area 320 x 320, 14,000 frames @ 122 fps. Processed in AutoStakkert and Registax, plus a little polishing in Lightroom. 

Viewed Mars again last night, but under significantly better atmospheric conditions compared to the previous evening, which allowed a smaller capture area of 360 x 292 giving a larger image .

Attached is what is possibly my best Mars image of this apparition , taken through my 14 in Newtonian, ZWO ASI 462 Camera, and 2.5 x Powermate giving f12.5,  2 minute exposure, approx 16,000 frames at 130 fps, processed in AutoStakkert (stacked best 25%), and Registax, plus a bit of polishing in Lightroom. 

Incidentally, I always like to display images of Mars in the traditional astronomical format with South at the top, as I am used to seeing the features that way up, with Jupiter and Saturn it does make so much of a difference. I think it was only after they started sending imaging spacecraft to the planets, they started displaying erect images with North at the top.

John 

Braved the weather last night, according to the thermometer in my observatory shed it was minus 8, and had a look at Mars.

Conditions were not ideal with quite a bit of unsteadiness, attach my best image of Mars taken through my 14 in Newtonian, ZWO ASI 462 Camera, and 2.5 x Powermate, 2 minute exposure, approx 10,000 frames at 90 fps, processed in AutoStakkert (sacked best 25%), and Registax, plus a bit of polishing in Lightroom. 

Superb

John

Would be interested to know how it compares with the Baader Hyperion Aspheric 31 mm, which has a similar APFOV.

John 

38 minutes ago, Owmuchonomy said:

If you wish to use a DSLR for planetary imaging it is possible.  However, you will only get decent results if your Canon has video crop mode (my 60D had such a setting).  This crops the sensor capture down to something appropriate for planets for example 480 x 640.  Then you need to take video and use Autostakkert to stack the best of your frames.  I also got better results with eyepiece projection  (rather than prime focus) using a Baader adapter to connect the T ring adapter directly to the eyepiece.  The best results I obtained were when I used a 15mm plossl on my 102mm refractor.  I have moved on to using a 9.25" SCT and and proper planetary cameras, it's much less faffing around and gives you decent focal length and small chips.

Second that about needing to use eyepiece projection with a digital SLR to get a decent planetary image size, although so many observers dismiss it as being rubbish these days.

John 

9 hours ago, nfotis said:

 

In short, planetary imaging (or "lucky imaging") is quite different from DSO imaging.

A rule of thumb for planetary imaging says you want f-ratio 4x to 5x the pixel pitch. So, with a 3nm pixel, you want f/12 to f/15 or so, with a 4nm pixel you want f/16 to f/20.

Hope this helps,

N.F.

It also depends on the effective focal length of your system, to get decent sized planetary images ideally you need to aim for an effective focal length of not less than around 3-4,000 mm (achieved with a Barlow if necessary), which is one reason quite a few planetary imagers favoured Celestron C14's as they give this sort of focal length without the need for further amplification with a Barlow.  Having said that as mentioned previously, I understand geoflewis still likes to use a 2x Barlow with his C14 and ZWO ASI 462 (pixel size 2.9 um) giving an effective focal length of nearly 8,000 mm at f22.

I regularly do planetary imaging with my Esprit 150 (as 90% of the time it gives sharper images than my 14 in Newtonian), using a 2.5 x Powermate, which gives an effective focal length of 2,650 mm @ f17.5. With my ASI 462 camera (pixel size 2.9 um), the formula also suggests that I would get better results with the cheaper ASI 224, which has a larger pixel size of 3.75 um, not sure whether this would be the case.

John 

3 hours ago, PeterC65 said:

I'm struggling to square this formula with the one used by the Astronomy Tools website, Resolution (ArcSeconds per Pixel) = Pixel Size / Telescope Focal Length x 206.265, where we should be aiming for a figure of 0.67-2"/pixel for average seeing conditions.

My main camera scope is a 72mm / 432mm refractor which with my IMX585 camera (2.9um pixel size) gives 1.38"/pixel, so ideal sampling for average seeing. But it is F6 so the formula given by @ONIKKINEN suggests it is far from ideal and I should instead be using my Mak!

Working this backwards, I would need the refractor to have an aperture of only 37mm to satisfy both formulae, so should I be stopping it down?

Neither the Mak nor stopping down the refractor makes any sense.

 

The formula given in Astronomy Tools is absolute rubbish, at least as far as Planetary Imaging is concerned, it suggests that with my Esprit 150 and ZWO ASI 462 under O.K. Seeing Conditions, I should be using a Focal Reducer rather than a Barlow.

geoflewis I gather regularly successfully uses f22 (2x Barlow), or even f26 with his C14 and ASI 462.

John 

45 minutes ago, Rallemikken said:

Check out the wavelet function in Siril if you already have that installed. Used it some. I do everything in Linux, and usually it's no problem running windows programmes under Wine, but Registax is the exception. Impossible, tried it with many distros.

I've never had a problem running Registax with Windows 10, although as I mentioned it can be slow if you use it for aligning and stacking.

John 

The sky unexpectedly cleared at about 23.00 last night, so thought I would have a quick look at Mars, conditions weren't too bad, but with some unsteadiness. A heavy dew however came down after opening my observatory shed, so I was limited to less than an hour of observing time.

Image taken through my Esprit 150, with my ZWO ASI 462 planetary camera, 2.5 x Powermate, 3-minute exposure, 28,000 frames giving 157 fps, processed in AutoStakkert, Registax and Lightroom. 

John  

48 minutes ago, Mandy D said:

I beg to differ. The smaller sensor does not capture a larger image for a given focal length. The size of image projected onto the sensor is dependent only on the effective focal length of the optical system.

Reducing the capture area of the sensor does not, in any way, change the image scale or number of pixels that the object of interest covers, hence no enlargement takes place. This equivalent to so-called "digital zoom" and is correctly known as cropping.

 

The images do however appear larger after cropping when you post them on this website, although they do appear the same size in Windows Photo Viewer, which confused me at first. When I posted my first Jupiter image (with Io shadow transit) on this site, I could not understand why it appeared so small compared to other observers' images, but it was because I had used the full capture area of my ASI 462 camera (no cropping), plus not used a Barlow.

John 

16 hours ago, wesdon1 said:

Thanks for advice John. I actually do have a SVBONY EP projector, but was still getting small planet ? I must be doing something wrong ? I have just ordered a ZWO ASI 120MM, to do mono planetary, and increase frame rates with software on my laptop. I am also going to experiment with different sized Ep's and see what works best. I am only 4 planetary imaging sessions in from total beginner status, so I am sure with practice and experimentation, I'll finally get my planets looker big and detailed! Thanks again John, i'd be lost without dcecent people like yourself on here!

Wes. 

You will get much better results with a dedicated planetary camera than with a digital SLR, not only does the much smaller sized sensor give you larger planetary images, but you can reduce the capture area of the sensor (or ROI) further to enlarge the image even more, which you cannot do with some digital SLR's. In addition, most planetary cameras enable frame rates of up to around 200 frames per second, whereas most digital SLR's are limited to around 30 fps.

I attach for example processed images of roughly the same area of Mars, the first was taken on 15 September 2020 (when the South Polar Cap was visible and Mars exhibited a 20 arc second disc) through my 14in Newtonian, using my Canon 6D digital SLR (which has a maximum frame rate of 30 fps) and eyepiece projection with a 9.7mm Plossl eyepiece. The second was taken through the same telescope on 13 November 2022 (when Mars exhibited just a 16 arc second disc) using a ZWO ASI 462 Planetary Camera (which I did not have in 2020) with a 2.5x Powermate giving an effective focal length of 4,500 mm at f12.5, the capture area being reduced from the full 1936 x 1096 to 544 x 548, and a 2-minute exposure of 13,000 frames at 111 fps. Images were processed in PIPP (for the one with the Canon 6D), AutoStakkert and/or Registax, plus Adobe Lightroom. 

The differences between the 2 images are quite obvious, both in terms of size and detail, despite Mars being further away in November 2020, and if I recall correctly more detail was visible through the eyepiece in September 2020. 

I should stress that I am a relative beginner to planetary imaging, my images are nowhere near as good as those of other observers such as Neil Philips, and I made all sorts of mistakes to begin with, such as using the full capture area of the camera and then wondering why my images still appeared very small. I've also tried enlarging the images in programs such as GIMP, but generally this did not seem to give very good results. 

John 

5 hours ago, wesdon1 said:

I actually started out with using the 8 inch reflector for planetary, but I have decided to use the refractors instead, because  I'm assuming it'll be easier framing them in post processing ? In the 8 incher, I'm finding it very hard to "zoom in" enough ? even with my SVBONY EP Projector fitted with a 9mm planetary EP ? The planets are STILL small in the final image ? I read yesterday that I should be using F20, up to F30 if the conditions allow, and my refractors are naturally longer FL's than my big f5 reflector. Obviously I'm a novice in imaging so please bare with me if I sound stupid!? LOL

Wes

It's not the focal ratio that determines image size, but the effective focal length, so your f5 8 in Reflector with a focal length of 1000 mm, will actually give you a slightly larger sized planetary image than your 80/90 mm f11/f10 refractors.

To get a decent sized planetary image even using a dedicated planetary camera with a small sized senor, such as the ZWO ASI 224 & 462, ideally you need an effective focal length not less than around 3-4,000 mm (which you would achieve with a 2.5 - 3x Barlow), one planetary imager in particular likes to use a 2x Barlow even with his C14 giving an effective focal length of nearly 8,000 mm at f22. 

Although some observers will disagree with me, in my opinion if you are using a digital SLR, then you will probably need to use eyepiece projection (which can provide greater amplification than a Barlow/Powermate) to get a decent image size. To those that disagree with me I would love to see some large scale detailed planetary images taken using a digital SLR, using no more than a 2-3x Barlow for amplification. If the initial image size is too small it can be difficult to achieve correct focus, and to obtain sufficient alignment points in processing software such as AutoStakkert and Registax.

I don't understand why so many observers rubbish eyepiece projection these days, it was the method commonly used 20 years ago before the advent of digital cameras. An observer recently posted on 'Cloudy Nights' some quite nice images taken with a small Takahashi Refractor, using a Baader Zoom eyepiece, coupled directly to his planetary camera. 

John