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A few things here: 1. Your exp time is too high, dial it way back as mentioned. 2. You may not have the camera sensor at the right focal point, backspacing relates to getting the sensor at the point of focus and usually applies when using a corrector lens prior such as a flattener, reducer or coma corrector. As I assume you may not be using any, the sensor therefore is not at the point of focus. You can test this very roughly by getting an eyepiece in a diagonal into focus, then swapping to the camera and adjusting focus nearby, itll need to be adjusted because an eyepiece will contribute to the focus point whereas a camera is relying on the focus point of the telescope only. But, if point (1) is not right, you'll never see the focus point. 3. Your telescope is a long focal length, so with point (1) all you'll see is a bright light, even if pointed somewhere off target but near the moon. The brightening is worse the longer the exposure time and your scope can be further away from target but youll still see a brightening on the camera. Potential solutions: A. Dial back the exposure to less than a second, not necessarily fractional ms or uS (micro seconds) at this point, this is what I do. Make sure the target is a white disc. Get to near your focal point, when you look on camera the bright disc will get smaller as you're approaching focus and larger when away. Then move the scope off target a little and repeat. The disc should get smaller and smaller, if you're near focus and your scope it pointed at the edge of the moon you'll be able to focus to a near sharp circle edge, this will get you extremely close to the focus point. B. Then dial back the exposure significantly to ms or uS exposure (most likely on the moon you'll use ms, uS is usually useful when doing solar). The bright disc will retreat to the moon colour, maybe a dim grey if the exposure it too short. The surface detail will show. Then very minutely adjust focus until areas of contrast are sharp as you can see, you'll have to work with the atmospheric seeing here and make a focus adjustment then assess when seeing "freezes" fractionally time to time. You'll have to to and fro a little here. The exposure should be such that your histogram peak isn't crushed to the left (you're "destroying" the darkest black/shadows areas merging them into one uniform blackest black, also known as clipping) and the whites/highlights also the same but on the RHS of the histogram. C. Try the camera with diagonal and without (straight through). Note the latter you may need spacer/extension/backfocus rings because a diagonal takes up that distance from the back of the scope up to the eyepiece and you have to compensate for that sometimes, or rack the focus on the scope further than it would be with a diagonal+eyepiece. You might find without the extensions you cant get focus when imaging straight through. D. Basic but be absolute sure your finder is aligned with the centre axis of your telescope, the finder will make it easier to ensure your camera is centred or slightly off target. With experience you can usually do without a finder and just use a deft touch with sweeping with your scope and using rough eye "finding". A larger camera sensor makes this bit easier, as well as not having to nudge the scope so much if you're not using a goto tracking mount to keep the target centered on camera.  

I agree re seeing is so important of course.  If a persons best view ever of, say Jupiter, was with a certain scope it doesn't mean its better than any other scope that wasn't available to compare it with at the time of the observation.  Even having a quality 5 inch refractor along with a quality 8 inch Newtonian and comparing them directly is flawed. The comparison would have to be on a night when the seeing is good enough that the larger telescope, can be used to perform to its best resolution as well as the smaller one.  If not then its not a fair comparison. Any differences would be more of a test of the observing conditions rather than the telescopes ability. So when I say that a such and such telescope gave me my best view ever of Mars, it may be interesting, but it doesn't meant it was the best planetary scope I've ever used.  It happened to be a 16 inch SC one early morning just before dawn, when the seeing was exceptional. The best person to answer the original question would be one who has owned both a 5inch refractor and 8inch Newtonion simultaneously over quite a few years.  Not only that, but they would have had to frequently used them side by side on numerous occassions when the seeing was good enough for both to perform to their respective maximum possible resolutions.  Oh yes, and on a good variety of targets. Any takers?    

This is one of the threads on CN which has several contributors some of whom appear to be very well experienced visual observers. They have used several higher end refractors visually as well. It was from this thread and others that I gleaned the visual performance of the 120/140 Askars was good. Have I been reading this thread through a pair of rose tinted glasses? Thanks. https://www.cloudynights.com/topic/900932-askar-140-apo/

I have thought about putting a hand warmer in my eyepiece case! I think the small size of eyepiece lenses is also relevant. Even the largest ones will be quite rigid compared a big floppy newt mirror for example.

Here is one of my old posts from 2010 where my wife and I visually compared a 5” refractor to a Skywatcher 8” F/6 Newtonian…   “I was really enthusing about how good the seeing was so Mrs Dweller25 decided to come out and have a look. Now this is a rare event as Mrs D and the cold night air don't mix so to spice things up a little I suggested a shootout between the 5" Takahashi FS128 and the Skywatcher 8" F/6 Newtonian. Each of us would take a turn observing and drawing Mars in each scope so we could compare and contrast. Seeing was very good - AII, temp was -4'C. We concluded :- 1. Mrs D25 has better eyesight than me - I have astigmatism 😕 2. The humble Skywatcher slightly outperforms the Tak 😱 🙂